Cannot get original callerid in attended transferred extension

Asterisk Asterisk Dialplan
1

Hello, community.
I have a question about the original caller’s information in a transferred call.

There are three endpoints (A, B, C).

When making a call from endpoint A to endpoint B, CALLERID(num) is for endpoint A and EXTEN is for endpoint B in the extension.

However, if you transfer this call to endpoint C using atxfer in features.conf, CALLERID(num) is for endpoint B and EXTEN is for endpoint C in the transferred extension.

Is there any idea to get the number of endpoint A in the transferred extension?

Thanks.