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Every voice agent needs a phone number to call from or to answer on. Callers supports four ways to provide numbers. You can start with a Callers-managed number in a few clicks, bring your own Twilio account, or connect the carrier you already use over a SIP trunk. You can mix options in one account. Each agent uses the numbers you assign to it.

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Compare your options

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Which option should I choose?

Choose this to test or launch quickly in the US without a carrier account. Buy a number from Phone numbers and assign it to an agent. Purchased numbers support both incoming and outgoing calls.
Choose this if your numbers, compliance registrations (such as A2P 10DLC or toll-free verification), or SMS already live in Twilio. Callers uses your Twilio account directly, so calls and messages appear in your Twilio console. If you use Twilio Flex or Elastic SIP Trunking, use the Twilio SIP guide instead.
Choose this to use an existing carrier contract, numbers outside the US, your own PBX or contact-center platform, or carrier-grade routing. SIP also unlocks features that need direct signaling access, listed below.
Connect Telnyx over a SIP trunk for voice calls, and connect your Telnyx account in the App Center to send SMS from the same numbers.

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Features that work best over SIP

Some features depend on SIP signaling, so they’re available, or work fully, only on calls over a SIP connection:

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Provider guides

SIP trunk setup

All SIP settings: authentication, gateways, headers, testing.

Twilio

Connect your Twilio account with an Account SID and Auth Token.

Twilio SIP

Elastic SIP Trunking and Twilio Flex.

Telnyx

Telnyx over a SIP trunk.

Plivo

Plivo SIP endpoints.

CommPeak

CommPeak SIP accounts.

Squaretalk

Squaretalk with IP authentication and a tech prefix.

Phone numbers & caller ID

Assign numbers, dialing strategy, and spam checks.

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After you connect

  1. Open Phone numbers to check that your numbers appear under the right source.
  2. Assign numbers to an agent in its phone number settings. Outbound agents rotate across the numbers you select. Inbound agents answer on the numbers you assign.
  3. Place a test call in each direction before going live.
Some countries restrict caller ID or require local numbers for outbound calls. Check your carrier’s rules for each destination before launching an outbound agent.

Phone numbers and caller ID

Assign numbers to agents, rotation, local presence, and spam checks.

SIP trunk setup

Connect your own carrier or PBX over SIP.

Call transfers

Cold and warm transfers, SIP headers, and SIP REFER.

Callers for Enterprise

Dedicated telephony setups, custom limits, and rollout support.