If you are building a VoIP proposition for business clients, the SIP carrier you use has a more significant impact on the end result than most resellers initially expect. The carrier determines call quality, billing model, international capability, number porting reliability, and what happens at the network level when things go wrong. X2 works with two carriers — Telnyx and Voiceflex — and this guide explains the difference and when each is the right choice.
What Is SIP Trunking?
SIP trunking is the technology that connects a business phone system — such as a Yeastar P-Series PBX — to the public telephone network over an IP connection. Where traditional ISDN used dedicated physical lines, SIP trunks are provisioned as a service on the PBX and route calls through the carrier’s network via the business’s broadband connection. A SIP trunk is sold as a number of concurrent call channels, with geographic and non-geographic numbers assigned to the trunk.
Telnyx: Private Network, Global Reach, AI-Ready
Telnyx operates its own private global IP network rather than routing calls over the public internet. The practical result is more consistent and predictable call quality — particularly relevant for high-volume environments, clients with international call traffic, or sectors where audio quality matters commercially.
- Per-second billing: Clients pay only for actual call time, with no rounding. A cost advantage for businesses with high volumes of short-duration calls.
- International virtual numbers: Available in 140+ countries — viable for clients with multi-territory operations who want local presence without overseas infrastructure.
- AI voice capability: Telnyx’s platform supports intelligent inbound call handling — routing, qualification, and automated resolution — increasingly relevant to the UK SME market.
- Direct infrastructure ownership: Telnyx owns and operates its network, meaning faster fault isolation when issues occur at the carrier level.
Voiceflex: Established UK Tier-1 Carrier
Voiceflex is one of the UK’s established wholesale voice carriers, with a particular track record in number porting and UK-hosted infrastructure. For clients with large existing number estates — DDI ranges, freephone numbers, or complex porting requirements — Voiceflex’s porting process is well-tested and consistently managed.
- UK Tier-1 carrier pedigree: A familiar name in the wholesale channel with a long operational history.
- DDI management: Strong tooling for managing large number estates and complex porting cases.
- UK-hosted infrastructure: Voice traffic handled within UK data centres — relevant for clients with data residency requirements.
- Geographic resilience: Redundant UK infrastructure with failover built in at the carrier level.
Which Carrier Is Right for Your Client?
Both are solid options, and the right choice depends on the client profile. Telnyx tends to be the better fit for clients prioritising consistent call quality, international reach, or interest in AI-assisted call handling. Voiceflex tends to be the better fit for clients with large existing UK number estates, straightforward domestic requirements, or where UK carrier familiarity matters in the commercial conversation.
X2 handles all provisioning for both carriers. You don’t manage the technical relationship with either — we configure the trunks, coordinate number ports, and support network-level issues under your brand. When you bring us a new deployment, we’ll ask a few questions about the client’s usage profile and recommend the appropriate carrier. To discuss a specific client scenario, speak to the X2 team.