FLEXIBLE UK SIP & IAX2 TRUNKING
Flexible UK SIP trunks for your system.
Bring your PBX, softswitch or voice application. Numbers cost £2 per month, every account includes one complimentary channel, and inbound calls are free.
No card required. Prices exclude VAT.
Works with your stack
OpenAIElevenLabsLiveKitVapi
CONNECT YOUR WAY
One network. Three straightforward ways to connect.
Sipflex provides the UK numbers and PSTN connectivity. You control the PBX, softswitch or application at the other end.
SIP registration
Register using your Sipflex phone number or username and separate trunk password.
Registration settingsIP peering
Authenticate by IP address, with primary and failover peer configuration for production systems.
Peering settingsIAX2
Connect Asterisk and compatible platforms using IAX2, with simple NAT and firewall requirements.
Explore IAX2FLEXIBLE PRICING
Build the SIP trunk you need.
No packages and no per-user pricing. Select your numbers, concurrent capacity and calling option.
Choose your setup
BUILT FOR SELF-SERVICE
For people who know what they want to connect.
Choose the route that matches your system. The service stays the same: flexible UK numbers and trunk capacity without a bundled PBX.
PBX administrators
Connect Asterisk, FreePBX, 3CX or another SIP-compatible system.
Developers and AI voice
Add UK phone numbers and PSTN connectivity to the application or platform you are building.
Production and high volume
Discuss capacity and volume pricing for an established application with significant traffic.
BUILT FOR OPEN TELEPHONY
Asterisk is not an afterthought.
Use modern PJSIP registration, IP-authenticated peering or IAX2, backed by detailed configuration guides and copyable examples.
- PJSIP registration
- IP-authenticated peering
- IAX2 registration
- TLS and secure media options
- Codec and DTMF configuration
PLATFORM PROFILES
Skip the platform-specific SIP setup.
Choose a profile in the Sipflex portal and we apply the SIP settings that platform expects — registrar, transport, codecs and related options.
Profiles simplify SIP configuration. They do not create or manage your account with the selected provider.
AUTOMATE YOUR TELEPHONY
Manage Sipflex programmatically.
Provision numbers, change capacity, configure routing, retrieve call records and receive real-time call events through the API.
- Dedicated API credentials
- Number and channel management
- CDRs and account usage
- Call-event webhooks
{
"action": "Get-Channels",
"context": "account"
}
{
"Status": "Success",
"Data": {
"IncludedChannels": "1",
"ExtraChannels": "7",
"TotalChannels": "8"
}
}DOCUMENTATION-FIRST SUPPORT
Clear settings. Clear responsibilities.
We document Sipflex service settings and can advise on provider-side questions. You remain responsible for your PBX, firewall, devices, dial plan and application.
Browse configuration guidesSerious controls behind a flexible service
Comprehensive KYC and fraud controls help protect legitimate accounts from unexpected or unauthorised traffic.
- Identity and usage verification
- Spend and destination controls
- Caller-ID controls
- Active fraud monitoring
PRODUCTION TRAFFIC
Running an established high-volume application?
Tell us about the platform, destinations and expected usage. We can discuss capacity and volume pricing.
30-DAY FREE TRIAL
Connect your system to Sipflex
Start testing with your own PBX, application or voice platform.
No card required.