Help with Asterisk: Logging attended transfers

[Ret]

Yes, transfers are done correctly by the phones but the logs are not entirely correct.
The reason is that transfers by phone buttons rely on pure SIP protocol they don't use Asterisk built-in version of attended transfers (*2).
In the case you mention "If A calls B, B answers the call , A and B are in the call , A tells B that A want to find C
B presses Transfer +C's number to make a call to C, C answers the Call, B then presses the Tranfer button to finish the transfer, now B back to idle states, and A and C are in the call."
My Asterisk logs show an entry showing call from A to B, and then another call (with another Source channel ID) from B to C. So we cannot infer that a call from A to C has been made.

Unattended transfer, on the other hand, show up just fine on the logs. There's an entry showing call A to B and then another entry showing a call from A to C (Showing the same source channel ID). This way we can, at least infer, that the same source channel was transferred to C.

I know this is a question more on Asterisk than on the phones, but maybe people here know have experienced the same and know the answer.
Thank you for responding!