пусть берут DID из TO
[custom-get-did-from-sip]
exten => s,1,Noop(Fixing DID using information from SIP TO header)
exten => s,n,Set(pseudodid=${SIP_HEADER(To)})
exten => s,n,Set(pseudodid=${CUT(pseudodid,@,1)})
exten => s,n,Set(pseudodid=${CUT(pseudodid,:,2)})
exten => s,n,Goto(from-trunk,${pseudodid},1)