Seems that my sip lrovider allow to transfer calls only to extensions using #2EXT - but the transfer call tool not allowing to type # Is there any way to transfer the call using #2EXT instead of a number ?

Vapi’s transferCall tool doesn’t support dialing #2EXT directly, but you may work around it by using the extension field (if your SIP provider accepts it) or setting up a dynamic webhook transfer that can insert custom logic like #2EXT..

I cant find any integration on make of my VOIP provider.. do you know maybe how can I do this ?

Set up a BYO SIP trunk, then use Make.com with Vapi’s webhooks and actions to handle dynamic call routing and transfers.. https://docs.vapi.ai/advanced/sip/sip-trunk