> ## Documentation Index > Fetch the complete documentation index at: https://docs.anyreach.ai/llms.txt > Use this file to discover all available pages before exploring further. # Phone numbers and telephony > How numbers, trunks, and agents connect to place and receive calls. A phone number is the entry and exit point for voice calls. Each number carries two independent slots — one inbound agent version and one outbound agent version — and is attached to exactly one trunk that brokers connectivity to the carrier. Calls flow over SIP through LiveKit, so the same number can answer incoming calls with one agent and originate outbound calls with another. ## The model Three objects make up the telephony layer: | Object | What it is | | ---------------------- | ------------------------------------------------------------------------------------------------------------------- | | Phone number | A purchased or imported number with independent inbound and outbound agent slots. Belongs to one trunk. | | Trunk | A SIP trunk that connects your org to a carrier. Either Anyreach-managed (Twilio) or bring-your-own-carrier (BYOC). | | Inbound routing config | An optional per-org workflow that decides which agent answers an incoming call at call time. | A phone number record (`/core/phone-numbers`) has two slots that are set independently: | Field | Type | Default | Description | | --------------------------- | ------ | -------- | ------------------------------------------------------------ | | `inbound_agent_version_id` | string | none | Agent version that answers calls to this number. | | `outbound_agent_version_id` | string | none | Agent version used when this number places calls. | | `trunk_id` | string | required | The trunk that carries calls for this number. | | `outbound_shareable` | bool | `false` | Whether the number can be used as caller ID by other agents. | Setting one slot does not affect the other. A number can answer inbound calls without ever placing outbound calls, and vice versa. ``` Caller ──▶ Carrier ──▶ Trunk ──▶ LiveKit SIP ──▶ inbound agent version Outbound ◀── Carrier ◀── Trunk ◀── LiveKit SIP ◀── outbound agent version ``` Agents are reached over SIP. Each org has a dedicated inbound trunk that hosts agent SIP endpoints of the form `sip:@`, and LiveKit bridges the carrier leg to the agent leg. ## Trunks: managed vs BYOC Every number sits on a trunk. There are two kinds. | | Managed (Twilio) | BYOC | | ---------------------- | ----------------------------------------------- | ---------------------------------------------- | | Provider | Anyreach-operated Twilio account | Your own SIP carrier | | `managed_account_id` | set | not set | | How numbers are added | Bought through Anyreach (`purchase-number`) | Imported onto the trunk you create | | Created/edited via API | No — managed trunks are provisioned by Anyreach | Yes — `POST /core/trunks` | | Best for | Getting started quickly with US local numbers | Keeping existing carrier contracts and numbers | Managed trunks cannot be created, updated, or deleted through the API, and you cannot create a phone number directly against a managed trunk — buy numbers through the managed account instead. BYOC trunks you own are fully editable. A BYOC outbound configuration carries the carrier's SIP details: | Field | Type | Default | Description | | ------------------ | ------ | -------- | ---------------------------------- | | `address` | string | required | Carrier SIP host to send calls to. | | `auth_username` | string | required | SIP auth username. | | `auth_password` | string | required | SIP auth password. | | `transport` | enum | `UDP` | SIP transport. | | `media_encryption` | enum | `NONE` | Media encryption setting. | ## Getting numbers There are two ways to get a number onto a trunk: Search the shared Anyreach Twilio account and purchase a number. Search defaults to `country_code` `US` and number type `local`; the search filters voice, SMS, MMS capability, area code, region, and postal code. Purchased numbers land on your managed trunk automatically. Create a trunk pointing at your own carrier, then create phone number records against it. Use this to bring numbers you already own onto Anyreach. ## Inbound routing Once a number has an inbound agent version, every call to it reaches that agent. For static routing, that is all you need — the number maps to one agent. For dynamic routing, configure an inbound routing config for the org. It runs a `workflow_definition` at call time to pick the agent, with a `fallback_agent_id` / `fallback_agent_version` used when the workflow does not select one. There is one config per org, and it has an `enabled` flag (default `true`). | When to use | Choose | | ----------------------------------------------------------- | ----------------------------------------------------- | | Each number always answers with the same agent | Static — set `inbound_agent_version_id` on the number | | The answering agent depends on caller, time, or other logic | Dynamic — enable an inbound routing config | ## Next steps Search the Anyreach Twilio account and purchase a US local, voice-enabled number. Set the inbound and outbound agent-version slots on a number. Route incoming calls statically or with a routing workflow. Bring your own carrier with a SIP trunk and import existing numbers.