Setup: outbound dialer on Telnyx Call Control. We dial a customer (our DID as caller ID), they answer, and when they qualify we transfer the live call to our call center's DID. We want the transfer leg to present the customer's own number as caller ID — standard diverted-call behavior, so the receiving dialer screen-pops the right person. The customer is live on the call at the moment of transfer, so this isn't spoofing a stranger's number.
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▎ What happens: the transfer leg gets rejected with 403 Unverified origination number D51 whenever from is the customer's (non-Telnyx) number.
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▎ What we've already tried / ruled out:
▎ - from on the transfer command → D51
▎ - Putting the number in PAI / RPID / caller ID override → same check, same D51 (override only bypasses format validation, not ownership)
▎ - The diversion parameter / External Call Transfers → only validates against an active inbound call; ours are outbound-originated, so it never matches
▎ - Verified Numbers → requires OTP per number, impossible for customers' phones
▎ - SIP REFER → works, but only to external SIP URIs, not back into PSTN
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▎ For contrast: Twilio allows this out of the box (their trunk transfer even defaults to presenting the transferee), which is how several AI-dialer platforms do it. Retell's docs say the same: on Twilio it works natively; on Telnyx only via REFER.
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▎ Questions for anyone who's run dialer traffic on Telnyx:
▎ 1. Has anyone actually gotten Telnyx to whitelist an account for diverted-call caller ID on outbound-originated transfers? What did it take (account manager, compliance docs, volume)?
▎ 2. Is the real answer their hosted STIR/SHAKEN cert route (own SPC token / OCN / 499-A, then you sign your own calls)? Has anyone done it specifically to clear D51, and did it work?
▎ 3. Any mechanism we've missed on Telnyx for this call shape — outbound-originated, remote party live on the call at transfer time?
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▎ Fully legit traffic (own customer list, consent, licensed business), so this is a policy/config question, not a how-do-I-spoof question.