Looking to move from ISDN to Hosted Voice?

Move pain-free with SAS Voice Services, our portfolio of managed voice and SIP services. 

You may be relying on a traditional analogue of IP based private branch exchange (PBX) telephone system. If so, it could be time to consider moving to a hosted solution in order to benefit from what a cloud-based solution has to offer.


What is it?

Hosted telephony is a telephone system that resides in the cloud rather than on customer premises. Calls can be made with a physical telephone or by a softphone on a PC / Laptop, Tablet or Mobile. Calls are made and received over the internet or private Wide Area Network (WAN) connection, via a Hosted Voice telephony system.  External calls are routed from the Hosted Voice system, via SIP Trunks, to the PSTN and cellular networks.  

  • Data travels from IP source to IP destination for internal calls or breaks out to the PSTN for calls outside of the company. It could be another handset on the hosted telephony estate or a landline in another country.
  • Think of SIP trunks as virtual phone lines. The use of SIP trunks removes the need for dedicated telephone lines such as ISDN. The concept of a phone call doesn’t change. It simply gets routed over data networks.
  • Hosted Voice services remove the need for a business to install or configure any equipment. You could think of it as a data centre housing everything on one huge telephone system, with a separate partition for each customer.

Why Hosted Voice?

Cost Reduction

Since Hosted Telephony uses SIP trunks, there are no ISDN lines required, which can have a massive cost impact.

  • You could save up to £9,000 per annum by dispensing with an ISDN30 (whose rental costs £25 per channel per month for each of 30 channels).
  • Against this, you would need additional bandwidth on the data connection to the Hosted Voice system.  One should allow around 100kbps per voice call, so for 30 channels we will need an additional 3Mbps.  This will add approximately £100 per annum to a typical internet circuit, which is a tiny fraction of the ISDN30 rental saving.
  • There is also a potential saving on the call charges, especially for businesses using BT.  As an illustration of these savings, BT will typically apply a call setup charge and a minimum call charge and will then round up the final cost of the call.  An SAS hosted voice service will avoid the call setup charge, the minimum charge and the rounding up, which potentially saves up to 50% on call charges, in addition to the fact that internal calls are free.  
  • Businesses who want to keep their on-premise PBX can still use SIP trunks to replace ISDN. And you can even keep your numbers. We can help with that.
  • Note that BT intends to stop new supply of ISDN from 2020 and phase it out by 2025, so businesses need an alternative!
  • No on-site equipment and equipment maintenance contracts are required.
  • There are free calls between all sites on the network (on-net calling). 


  • Legacy phone systems may not have the latest technology and may not easily be upgraded or integrated to the business systems. Hosted services, on the other hand, provide an enterprise system on a pay as you go basis, and one that is constantly being upgraded with the latest features.
  • Hosted Voice services have intuitive interfaces that people find easy and quick to use, which reduces wasted time.
  • Hosted Voice services help one to avoid missing calls. “Find me, follow me”, call diversion and overflow groups help people answer the phone every time.
  • Instant messaging, presence and virtual meetings all streamline teamwork.
  • “Presence” shows where people are so that one can reach them easily.
  • New functionality can be trialled quickly on a limited basis and then rolled out as and when needed (or discarded without commitment).


Hosted Voice is provided as a consumption model which can scale up and down. There is no need for additional line cards or servers as one adds users. 

Hosted voice offers capacity when required. Licences can be increased and decreased on a monthly basis, and the business is always on the latest software level with the latest features and predictable costs.



Hosted Voice simplifies integration into third party applications such as Office 365, Skype, call recording and video conferencing. 

A hosted system will have APIs but importantly, the system will be at the latest software level, which simplifies integration. 
Broadsoft (the hosted voice platform that we use) specifically focusses on having an open platform that supports integrations from best of breed software.

Disaster Recovery

Calls can be routed to a more appropriate destination, such as a remote office or switched to mobiles where staff can easily access their calls.


Fast configuration for new users and new sites, because there is no need to install and configure a new PBX at each site.

Are you moving to Microsoft Teams?

Would you like to seamlessly integrate Microsoft Teams with your voice platform? 

Get in touch to find out how.

Make an enquiry

3 steps to building your new hosted voice solution

With over 500 features, the functionality of the system can be overwhelming, so SAS combines different features into bundles to create a range of user licences; from a basic dial tone, which may be used for a conference phone moving up to office users who require voicemail. Soft clients on laptops that allow for Instant Messaging and screen-sharing provide a richer collaborative experience whilst remote workers can take advantage of Mobile, Desktop and Hot Desk licences providing them a consistent functionality across multiple mediums, allowing them to make and receive calls regardless of their location.

Choose your add ons


Phones and headsets are not a prerequisite, as users can use their PC or Mobile client to make and receive calls, however, the handset and headset are still prevalent on office desks, providing a richer quality of experience.

SAS provides a range of desk phones and headsets, as well as wireless handsets that are ideal in locations where mobility is key.

Desk phones

We offer a range of desk phones by Polycom and Yealink, with basic phones up to executive varieties with colour touch screens.

Conference Phones

SAS offers conference phones, again, from Polycom and Yealink, suitable for small meeting/huddle rooms up to large conference rooms. Entry level solutions support Audio Conferencing only, whereas more sophisticated models can be expanded to incorporate multiple auxiliary microphones and video. 

Wireless Handsets

For many Customers, the requirement to make and receive calls whilst away from their desk outweighs the additional functionality that comes with a fixed desk phone. SAS provide a carefully chosen set of vendors and solutions covering handsets attached to a single wireless hub to more sophisticated solutions that allow handsets to roam across 40 meshed base stations either on a separate DECT network or using an existing WiFi solution, normally used only for data.


For call centres or employees who simply spend a lot of time on the phone SAS provide a range of Jabra corded and wireless headsets compatible with Yealink and Polycom handsets as well as a USB version for your computer.

SIP Trunking is much more than just an ISDN replacement. SAS offer the next generation of SIP Trunking to either support our hosted telephony solution or complement your existing on premise PBX.

We provide SIP Trunks direct from our BroadSoft platform, therefore enabling all of the hosted features to be delivered over the SIP Trunk. Key solutions such as Disaster Avoidance features to Call Analytics and Call recording can complement the premise solution and enable a hybrid model for easy migration to hosted telephony.

SAS can connect you to the BroadSoft platform and onto the PSTN in a number of different ways; either by using your existing Internet connection, taking into consideration the type of connection you currently have and the number of concurrent calls you require; via a new internet connection provided by SAS or via a private connection to the SAS network where we directly peer with the PSTN.

Unlike traditional ISDN (which is due to be phased out by Openreach by 2025), SIP Trunking is not limited to a maximum of 30 concurrent calls per connection. Nor are they restricted to just providing voice calls.

The SIP Trunking service can co-exist with your internet or private WAN connection making this more cost effective to combine multiple services on one access compared to ISDN which can only be used for telephony.

Why buy Voice Services from SAS?

Combined Voice, Data and infrastructure expertise

Voice is a critical but sensitive application on the network:  It underpins business conversations, but the user experience of these conversations degrades badly under poor performance conditions.

SAS is an acknowledged expert in managing performance-sensitive applications such as voice, with many years’ experience, award-winning monitoring and many satisfied customers.

When SAS manages voice as well as network, we can offer

  • Peace of mind from controlling both the application and the network over which it runs;
  • Confidence from having one organisation accountable for end to end service and one account team and service desk who can understand the whole environment;
  • A holistically designed and implemented telephony, LAN and WAN solution that works together seamlessly;
  • Support for the whole IP path: The phone on the desk, the LAN that it’s connected to, the WAN that routes to the Hosted Platform, the platform itself and the SIP trunks that carry calls to the outside world;
  • A complete support service including patches and upgrades, Adds, Moves and Changes, Faults, planned engineering works and warranty management;
  • Simplified, combined reporting and management;
  • A better commercial arrangement;
We also have skills in infrastructure and can help integrate with Microsoft services such as Office 365 and Skype.


Features can be added or removed at any time, offering a granularity of service that matches each of the customers’ users to perfection.
Flexibility for changes of business structure and call volumes, and user profiles.


We use the world renowned Broadsoft platform. It is owned by Cisco, is a crucial plank in their software as a service portfolio and reflects their strategy to provide highly resilient network and cloud-based services that mitigate against large scale, capital investments.

We offer a stable, secure and scalable solution, consistent at all locations.

We offer seamless transition of existing equipment and services to the SAS infrastructure.

We keep firmware to within two firmware revisions to ensure full vendor support.

Peace of Mind

We are hugely confident in this service because we use it ourselves.

We are Business Continuity (ISO 22301) certified.  This ensures that we develop, implement and maintain resilient business continuity plans.

We are also Quality (ISO 9001), Health and Safety (OHSAS 18001) and Information Security (ISO 27001) certified. 

We hold major partner accreditations with many of the Tier 1 network carriers and Cisco.
In the last ten years we have successfully completed more than 16,000 highly commended infrastructure projects for business customers around the world.

SAS Voice Clients

We provide hosted voice services for many organisations as well as the voice and unified communications for our own business. We have in excess of 3500 end users under management.


Please see our case study about the voice and data network service we provide for Digraph. 

  • Digraph is a leading UK-based auto parts distributor for HGV trucks and trailers.

  • The voice solution is based on the Cisco Broadsoft platform, which operates as a SIP trunk, removing the need for phone lines and delivering a unified comms experience.

  • We also delivered a data network based on a secure, encrypted direct Internet solution with a DMVPN, to provide a secure tunnel from sites to HQ, and direct internet connectivity for cloud resources.
  • "We’ve gone from 13 branches to 23, and added SAS monitoring and added failover, yet the cost per month is the same"

"Previously, we didn’t know how many calls we were making. Now we know the number of inbound and outbound calls at a branch.

It really helps us a lot – we can see which sites need improving, where we’re losing business and where we can make more sales.

For a company relying on phones to make sales, this is a real solution!"

Hosted Voice commercial benefits

The hosted software as a service model helps you move your spend from Capex to Opex.

Hosted Voice uses SIP Trunks.  It:
  • Reduces ISDN costs
  • Reduces on-site hardware and maintenance contracts
  • Potentially reduces call charges
  • and allows free on-net calls between sites.

Don't feel ready to switch from an on-premise PBX?

  • You can still benefit from SIP!
  • The SIP trunks can simply replace your ISDN.  
  • It is very easy to set up a trial to route some of the calls over SIP rather than ISDN.

Hosted Voice can deliver the increased productivity of modern voice services while enjoying a flexible payment model and a cost neutral or better deployment.

How much money could you save by moving to SAS?

Send us your current bill and we'll provide you with a comparison price.

We have created a calculator to help compare your current call spend against the same profile on the SAS Tariff. This is especially useful if you're thinking of moving to SIP Trunking.

If you fill out the form and upload your call data, we can run it through our calculator and talk you through the results.

Find out more - no pressure!

If you would like to find out how this solution could benefit your business then 
please make an enquiry and we'll get back to you as soon as possible.

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