Hi Parth0774,
- If you’re using a Vapi number, outbound transfers show Vapi’s number as the caller ID by design. To preserve the customer’s number as the caller ID you must use a BYO (Twilio) number or import your own number via Twilio. See phone number import:
https://docs.vapi.ai/phone-calling
- Warm transfer voice/context behavior: warm transfers that play a spoken message before connecting only work fully with Twilio. With SIP/BYO providers, warm-transfer messages are placed in SIP headers and may not be voiced—check your SIP provider for support of custom SIP headers (see related notes in the transfer warm-transfer docs).
- Cold vs warm: you can configure transfer mode in the transferCall tool (blind = cold by default, or warm-transfer-\* modes). For full agent-voiced warm transfers and caller-ID preservation use Twilio numbers (or import Twilio numbers into Vapi). See call forwarding and warm transfer modes:
https://docs.vapi.ai/call-forwarding