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SIP Trunks and Inclusive Calls

A cost-effective and flexible alternative to ISDN with inclusive calls.
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Cost-effective Technology for a Mobile Workforce

SIP trunking offers a future-forward solution enabling business agility, scalability and immediate cost savings, up to 50% online rentals and 25% or more on call costs.


Inclusive calls with SIP Trunking will you save on your line rental and call costs with free call termination to UK fixed destinations, including 01,02 and 03 number ranges, providing free calls between connected sites, including international locations.

Highly Scalable

As a virtual solution, SIP trunks are ideal if you are moving, upsizing or downsizing and want to keep your existing numbers. Scale-up lines during busy periods and back down again afterwards. You can add lines, take them away, split calls at any time. You are always in control.

Number Flexibility

SIP Trunks support business relocations by enabling a geographical number to be retained without call forwarding costs ensuring business continuity and savings on advertising costs.

Business Continuity

SIP trunks can handle emergencies easily. They are inherently disaster recovery/business continuity ready, letting you reroute calls to an alternative location quickly and easily.

Phone Hacking and Misuse Protection

All your existing business numbers are protected from hacking and abuse of business telephone, bringing you peace of mind.

Affordable Resilience

Our active/standby and load sharing designs are engineered to cope with any situation to maintain telephone uptime.

High-quality Audio

Depending on the audio codec used, SIP can deliver speech quality that is on par, or better than, ISDN.

SIP Trunk Call Manager

SIP Trunk Call Manager offers a comprehensive suite of inbound call handling tools, ideally suited to those businesses who place a high value on Customer Service and are looking to manage incoming sales enquiries effectively.


SIP Trunk Call Manager inbound call handling features can be tailored to every individual’s needs and adapted instantly via the web and App control. Features include call queuing, IVR, voice mail, day and time routing, advanced statistics, date routing and notifications.

Disaster Recovery

With pre-built DR call routing, calls will failover ensuring calls are never missed and business never lost.

Future-Proof Communications

Replacing ISDN saves up to 50% on line rental and 25% on call costs whilst providing additional flexibility.

Inbound Empowerment

Full control of your SIP numbering routing anytime, anywhere from a desktop or mobile client.

Quick Number Allocation

New numbers can be allocated to your SIP Trunk Call Manager account with your required call plan within the same day.

How can we help you?

Below you will find the answers to the questions we get asked most frequently about. If you can’t find the answer you are looking for please contact us.

Questions About SIP Trunks

Will SIP work with my existing phone system?

If your phone system is new, it is likely you will have the capabilities to connect SIP trunks without too much fuss or cost. What you may need is an additional SIP card or licenses which you will need to obtain from your phone system supplier or Maintenance Company. If your phone system cannot support SIP then now may be the time to look at a hosted solution. We have 1000’s of users currently enjoying the benefits of Horizon today.

Why use SIP instead of traditional ISDN?

A SIP Trunk is carried across your existing data network. This removes the requirement to have expensive BT Openreach line rentals. SIP trunks are more flexible than normal PSTN lines. They allow you to present multiple numbers to your customers, and the number your business uses day-to-day is not subject to your location – it can be any number.

What connection do I use for SIP?

Whilst you can run SIP Trunks on any data connection we recommend using one of our designed data circuits, either assured IP, converged or Ethernet. SIP calls require bandwidth, and if you do not have sufficient bandwidth on your existing data circuit it is likely you will experience disconnected calls and jitter.

Is SIP cheaper than ISDN?

Generally the answer would be YES. SIP trunks are cheaper than ISDN30e and ISDN2e line rental, and call costs are lower when utilising SIP trunks, including zero cost site-to-site calls. However what is sometimes overlooked is the internet connectivity to deliver your SIP calls. As mentioned in the SIP reliability question, to try and push SIP calls across a low-end data connection could have a disastrous impact on your business.

How reliable are SIP trunks?

Providing you choose the right partner, YES. SIP calls can become problematic if:

  • The data connection cannot support the number of concurrent calls
  • The SIP network is not reliable with the necessary failover equipment
  • The end user equipment is not up to date to support your SIP trunks

We ensure that our solution will work within your environment before we put pen to paper. We offer data connections that suit your expansion rates, our SIP partner is the largest provider of VoIP in the UK, and should your phone system not be up to the task we can recommend our hosted solution, Horizon.

Can I move my existing business number to SIP trunks?

In most cases, YES. Geographic number porting is quite simple and painless. We can port your geographic number from most Tier 1 carrier networks. 95% of the time customers port their geographic number from ISDN or analogue BT Openreach lines to our SIP trunking solution.

What is the preferred replacement for ISDN?

SIP Trunking is our preferred replacement for traditional ISDN. It connects your phone system to the PSTN via broadband, FTTC or Ethernet connectivity. Our SIP Trunks work seamlessly with each of the leading IP phone systems in the UK marketplace. Compared to ISDN our SIP trunking service is less costly per channel and more flexible in how and where geographic telephone numbers can be used. It’s also quicker to install and provision and, as standard, it delivers extremely robust business continuity.

How do I know what we will save as a business?

Our account management team will make a no obligation cost comparison of your existing ISDN services. We’ll provide your business with a presentation of transferring services like for like, whilst also advising what are the benefits of moving to SIP or a hosted telephony solution.

What is SIP Trunk Call Manager?

In a nutshell, it’s a bolt on service for our SIP trunks which offers an array of call control features and SIP trunk services.

What does “SIP trunk” mean?

SIP stands for ‘Session Initiation Protocol’ which is the protocol that controls setting up the call and tearing it back down again. A SIP trunk is a virtual telephony line that connects your office to the outside world using a data connection instead of an ISDN or analogue phone line. SIP trunks carry your voice calls like an ISDN circuit would, generally at a lower cost. SIP calls between two SIP-enabled sites are zero cost as the call remains on-net.

How do I know if my ISDN30e or SIP provider will allow multiple geographic numbers to be presented?

Your ISDN30e or SIP provider will need to have presentation type 3 or 5 enabled. BT Openreach, Virgin Media, Cable & Wireless are all fixed line providers that can support this service. If you find that you cannot present multiple geographic numbers, then it may be worth speaking to one of our sales team about transferring your services to us.

How do I know if my dialler can manipulate the outbound number presentation?

Your ISDN30e or SIP provider will need to have presentation type 3 or 5 enabled. BT Openreach, Virgin Media, Cable & Wireless are all fixed line providers that can support this service. If you find that you cannot present multiple geographic numbers, then it may be worth speaking to one of our sales team about transferring your services to us.

Can’t find what you’re looking for?

SIP Trunks and Inclusive Calls

A cost-effective and flexible alternative to ISDN with inclusive calls.

Pricing options for SIP Trunks and Inclusive Calls and related products

Inclusive Minutes

£6.75 per month

5,000 UK Landline Minutes

2,000 UK Mobile Minutes Inclusive per SIP Trunk

Inclusive Minutes Pooled Across Account


Simply SIP

£4.75 per month

Inbuilt Resilient Features

New Number Flexibility and Retain Existing Numbers

Cost Effective ISDN Alternative


Failover SIP

£3.75 per month

Active Standby and Loadshare Options

Reroute Calls to Alternative Endpoint Instantly

Low-cost Resilient Option


Technology built for your business


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Our Partners

Working with established UK partners to deliver industry-leading services.

Our Values

Approachable | Dedicated | Accountable | Professional | Trustworthy

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