Different Adresses in From Field

Hello @ all,

I have the problem that if I´m doing a call, sometimes I get the real address in From Field.
The DisplayName is the real Name of the account and the URI contains the real Number before domain.
“RealDisplayName” sip:UserName@mydomain.com
and sometimes I get from asterisk proxy for Displayname the connection in form of “user1 - user2” and
the URI is then sip:asterisk@mydomain.com.
Why I´m getting this different informations back from psoxy in the From Field?

The call is going about an Asterisk 1.4.10

Best Regards