In my company, calls to mobile phones are made through a trunk so that each extension goes out with its own number (for example, extension 321 launches calls to mobile phones with the ID 147852369321).
When I activate call forwarding on an extension to a destination outside the PBX (e.g. a mobile phone) it happens that the recipient loses the caller ID because they are shown their own office extension as the source of the call.
I will try to explain this with an example. Extension 300 (Alice) calls extension 301 (Bob), but Bob (301) is not at his workplace and the call is forwarded to Bob's mobile. Bob's mobile is displaying caller ID 147852369301 and I would like the caller ID displayed on the mobile to be 147852369300 (the extension that originated the call) instead of 147852369301 (the extension that forwarded the call)