What you're up against
- ISDN has been the backbone of UK business telephony for decades, but it's expensive, inflexible, and on its way out. Per-channel costs keep climbing, adding capacity means ordering new lines, and the technology is being retired across the country.
- Many businesses have invested significantly in their PBX systems, and they work well. The issue isn't the phone system itself — it's the lines connecting it to the outside world.
- Replacing the entire setup with hosted VoIP is one option, but it's not always the right one. If your PBX is doing the job, SIP trunking lets you keep it while modernising the connectivity underneath.
How we fix it
We connect your existing IP-enabled PBX to our SIP trunk infrastructure, replacing your ISDN lines with flexible, internet-based voice channels. You keep your phone system, your numbers, and your call routing — but with lower costs, more flexibility, and a future-proof connection.
We check compatibility, handle number porting, and manage the trunks through the Omnixi platform.
Key Features
Everything you need, nothing you don't.
How It Works
Audit
We review your current PBX, ISDN setup, and call volumes to confirm SIP trunk suitability.
Recommend
We propose the right number of channels and any connectivity upgrades needed.
Deploy
We configure the SIP trunks, port your numbers, and test everything end to end.
Manage
Ongoing monitoring, capacity management, and support via the Omnixi platform.
Audit
We review your current PBX, ISDN setup, and call volumes to confirm SIP trunk suitability.
Recommend
We propose the right number of channels and any connectivity upgrades needed.
Deploy
We configure the SIP trunks, port your numbers, and test everything end to end.
Manage
Ongoing monitoring, capacity management, and support via the Omnixi platform.
Who It's For
Businesses with an existing IP-enabled PBX that want to modernise their line connectivity without replacing the whole system.
Companies facing the ISDN switch-off who need a proven migration path.
Any organisation looking to reduce telephony line costs.
Transparent Pricing
SIP trunking is priced per channel with flexible terms. Most businesses see significant savings compared to their current ISDN costs. Contact us for a comparison quote based on your existing setup.
Frequently Asked Questions
Got questions? We've got answers.
01 Is my PBX compatible?
Most modern IP-enabled PBX systems support SIP trunking. We'll carry out a compatibility check as part of the initial assessment — if there are any issues, we'll tell you upfront.
02 How many channels do I need?
It depends on your concurrent call volume. As a rule of thumb, you need roughly one channel per simultaneous call. We'll analyse your call patterns and recommend the right number.
03 What's the ISDN switch-off and does this solve it?
BT is retiring the PSTN and ISDN network by 2027. SIP trunking is the direct replacement — it keeps your PBX working on modern infrastructure. Yes, this solves it.
04 Can I mix SIP trunks with hosted VoIP?
Absolutely. Some businesses use SIP trunks for their main office PBX and hosted VoIP for remote workers or smaller sites. We can design a hybrid solution that works.