Hello !!!
Nice to see that there is so helpfully forum!
I start read topics about how to change a Caller ID but can not find solution for me.
I am using Trixbox 2.6 , the problem for me is- when I put a call forwarding,to PSTN number, the call forwarding does not work, because it is trying to send wrong number, not my number but caller ID. In my SIP trunk is different PSTN number, which come from my provider.
Is there solution how to change incoming call ID to my outband CID, to make my forwarding work?
Thanks, hope someone fill help me 
!!!
In FreePBX 2.6 you can select ‘block foreign callerids’, that should solve the issue