Which BT products are supported?

BT One Voice, BT IP Connect (Public/Private), BT SIP Trunking, and most BT Business calling products. The integration pattern is the same: SBC + SIP entity for Open behind your PBX.

Do I have to change my BT contract?

No. The BT-side configuration stays exactly as it is. The change is on your PBX/SBC, not at the carrier.

Can I keep my UK numbers (0800, 0808, 03xx, geographic)?

Yes. All BT-supplied numbers stay on BT.

What about 999 / emergency?

999 routing stays on BT, fully unchanged. The AI never initiates 999 calls itself; it warm-transfers or passes through emergency intent.

Yes — for any BT SIP trunk, an SBC is the standard mediation layer.

Can the AI escalate to my PBX hunt groups?

Yes. SIP REFER returns the call via the SBC into the PBX, which routes to a queue or hunt group with the transcript attached.

What does this cost on top of BT?

BT keeps invoicing carrier minutes. Open charges per resolved conversation.

How long does setup actually take?

30–60 minutes — most of it is PBX/SBC change-control rather than the Open side.

SIP Trunk

Open for BT Business

Pair Open with BT Business SIP Trunking via your SBC and the AI picks up — BT keeps the carrier-of-record role and your existing numbers.

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Setup time: 30–60 minutes
Auth: SBC pairing (TLS + IP allowlist)
Directions: Inbound · Outbound · Call transfer
Pricing: Included with Open

01 — Overview

Can I add an AI phone agent to my BT Business SIP setup?

Yes. BT Business SIP Trunking, BT One Voice, and BT IP Connect are SIP-capable carrier products that already terminate on your SBC; Open joins as a SIP destination behind that SBC.

BT Business remains your carrier and SIP trunk provider. Numbers, regulatory compliance (Ofcom, 999 routing, 0800/0808 routing), and PSTN reach all stay with BT. Open joins as a SIP destination behind your SBC — the SBC keeps BT-side signaling cleanly mediated, and Open lives on the trusted side of it. The PBX you run behind the SBC (typically Avaya, Mitel, Cisco, 3CX, or a hosted Cloud PBX) decides which calls hand off to AI.

For inbound, the integration is two-layered: your PBX still receives the call from BT via the SBC, 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). BT signed off on 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 BT. BT-side billing sees regular outbound minutes; Open never marks them up. Caller IDs are constrained to whatever BT has approved on your trunk.

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 and detected intent attached.

999 / emergency stays on BT. The AI does not initiate 999 calls; it warm-transfers or passes through emergency intent to your existing path according to how the agent is configured.

What stays the same on BT Business

BT-supplied numbers
DIDs, 0800/0808 / 03xx numbers, regulatory bundles stay on BT.
BT contract and pricing
Your BT One Voice / IP Connect / SIP Trunking contract doesn't move.
Existing SBC
Your SBC keeps mediating BT-side signaling exactly as it does today.
999 emergency routing
Emergency calls keep using your BT-side routing.

What's new with Open

A SIP entity behind the SBC
Open's SIP URI becomes a destination on the trusted side of your SBC.
PBX-side routing change
Your PBX (Avaya/Mitel/Cisco/3CX/etc.) routes opted-in calls to the Open SIP entity.
AI handles the conversation
On opted-in branches, the AI greets, listens, calls your tools, and replies in natural speech.
Pricing model
Open per resolved conversation. BT keeps invoicing carrier minutes.

02 — Why this works

The native BT Business experience

BT contract untouched
Your BT One Voice / IP Connect / SIP Trunking agreement doesn't change. Open just rides on the trusted side of your SBC.
Per-PBX-route opt-in
Pick exactly which PBX hunt groups, ACD paths, or queues route to AI.
999 stays on BT
Emergency routing remains on the carrier side — the AI never initiates 999 calls itself.
Warm transfer back to your PBX
AI escalations come back via SIP REFER through the SBC into your PBX with the transcript attached.

03 — Setup guide

Wire up BT Business in 30–60 minutes

Two trunks — one inbound, one outbound. Both configurable from Settings → SIP in the Open dashboard.

1
Open Settings → SIP
Open the inbound trunk configuration.
2
Pick a SIP region
Choose EU (UK / Western Europe).
3
Copy the SIP credentials
Grab the SIP endpoint, username, and password.
4
Add a SIP entity behind your SBC
On the trusted side of the SBC, configure Open's SIP host as a SIP entity / trunk.
5
Wire your PBX to route opted-in calls
In your PBX (Avaya / Mitel / 3CX / FreePBX / etc.), add a hunt group / ACD path that routes to the new SIP entity for the branches you want AI on.
6
Add the matching numbers to Open
Under Phone Number (DID), add the BT DIDs that fronted the PBX route.
7
Assign numbers to an AI agent
Channels → Phone → Agents → assign DIDs.
8
Place a test call
Dial a BT-supplied number, take the AI branch, and confirm Open answers.

04 — Configuration

Settings → SIP, at a glance

A real inbound trunk for BT Business looks something like this. Yours are generated when you open Settings → SIP.

SIP entity · BT Business

Sample

Carrier: BT One Voice / IP Connect / SIP Trunk
Open SIP host: sip.eu.opencx.comEU region
Transport: TLSrecommended
Auth: TLS + IP allowlist (SBC)
999 routing: On BTunchanged

05 — Security

Encrypted, audited, refundable

SIP over TLS for signaling, SRTP for media. Every call is logged with full reasoning traces. SOC 2 Type II, GDPR-aligned, HIPAA- and PCI-ready. Backed by the Open $2M Refund Guarantee.

06 — FAQ