Open for AT&T Business

AT&T Business remains your Tier-1 carrier. Numbers, E911 records, regulatory compliance, and PSTN reach all stay with AT&T. Open joins as a SIP destination on the trusted side of your SBC — the SBC keeps AT&T-side signaling mediated, and Open lives behind it. The PBX you run (typically Avaya, Mitel, Cisco, 3CX, or a hosted Cloud PBX) decides which calls hand off to AI.

For inbound, the call lands on AT&T, traverses the SBC into your PBX, and at the point you want AI to take over the PBX routes the call to Open's SIP entity (also configured behind the SBC). AT&T owns the carrier leg; the PBX makes the routing decision; Open answers.

For outbound, Open opens a SIP session against the SBC using a service-account credential, and the SBC forwards to AT&T. AT&T-side billing sees regular outbound minutes; Open never marks them up.

What the AI does on the call: it listens, reasons over your knowledge base and connected tools, and acts. When the AI needs a human, it warm-transfers back via SIP REFER through the SBC into your PBX, which routes to a queue or skill with the live transcript attached.

E911 stays on AT&T. The AI does not initiate 911 calls; if a customer asks for emergency help, the AI warm-transfers to a human and passes through emergency intent to your existing E911 path.