Setting up Asterisk & Fritz!Box Router VOIP

I have an Asterisk 13 Server (&FreePBX) running on CentOS. I’ve created an
extension on Asterisk, named 444. Also, i’ve connected Fritz!Box router
(with VOIP) to extension 444 as a client. Now, it works
well, but the problem is that i cannot get the real number of the
caller. For example, if i have an incoming call to my Fritz!Box, it will
redirect it to asterisk 444 extension and I will get the client number (444), but not real caller’s number. Does anyone have any solution for this?

Make sure you haven’t specified callerid in sip.conf.

Obtain a sip debug trace and tell us where the caller ID appears in the INVITE.

If it doesn’t appear in the INVITE, this will need fixing at the FritzBox end.