i have user A with nummber 123, who is using a softphone with "xfer" funktion.
USer A calls User B (mobile phone nummber 0163X);
Asterisk sees CALLERIDNUM 123 and EXTEN 0163X
if the call is established, User A wants to forward User B to User C (with mobil nummber 0172X)
if User A press the xfer button and types in the mobilnummber of C (017x), asterisk sees the following
CALLERIDNUM 0163X and EXTEN 0172X.
now i want to check CALLERIDNUM. in the second call, User B to User C, asterisk must recognize, that 0163X in CALLERIDNUM is no SIP USer and Hangup the call.
so i want to disable the xfer feature.
how can i solve this?

dbget and figure out if CALLERIDNUM is known in astdb?