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Bind Voice Agents

  • Only when you bind agents to a number will the number be able to receive and make calls.
  • You can assign different inbound and outbound agent to the number.
  • You can leave agent unset to disable inbound / outbound (for example, you are doing outbound and don’t want callbacks, you can leave inbound_agent_id unset)
Phone number configuration showing agent binding for inbound and outbound
After binding an agent for inbound, you should be able to receive inbound calls already.

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Handle inbound overflow

Inbound calls count toward your workspace concurrency limit. To keep inbound calls available during high outbound volume, you can reserve part of your concurrency for inbound calls. See Reserved Inbound Concurrency. If all concurrency slots are in use, Retell briefly waits for a slot to open. If no slot opens after about 40 seconds, Retell transfers the call to the phone number’s fallback_number when one is configured. Without a fallback number, the call ends with concurrency_limit_reached.

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A/B Testing

See A/B Testing.

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Inbound Call Webhook

A lot of times, you want to use different agents to handle inbound calls of a number; also you need a way to provide dynamic variables to use for inbound calls, and other fields specific to that call. Read more at Inbound Call Webhook

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Inbound Custom SIP Headers

  • You can use custom SIP headers to pre-set dynamic variables for a call.
  • Retell extracts any header starting with sip.h.x-, along with common SIP headers like Diversion, History-Info, User-To-User and P-Asserted-Identity, and converts each into a dynamic variable by stripping the sip.h. prefix.
    • E.g. sip.h.x-caller: abc -> x-caller: abc
    • E.g. sip.h.p-asserted-identity: +12345678910 -> p-asserted-identity: +12345678910
    • E.g. sip.h.diversion: <sip:2000@192.168.254.254>;privacy=off;reason=no-answer;counter=1;screen=no -> diversion: <sip:2000@192.168.254.254>;privacy=off;reason=no-answer;counter=1;screen=no

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Get Call Detail

  • API: You can use Get Call API to get information like transcript, recording, latency tracking, etc.
  • Webhook: You can also setup webhooks to receive real time updates when call is initiated, ends, and analyzed. Read more at Call Webhook Guide.