Contact re-write after Redirect

My Asterisk calls are going to a redirect server that replies wit 302… etc. An in the reply the contact header field has the location of the actual server that im sending my calls to… however on the second INVITE, the contact header field is changed… it seems that if i compare the original request to the second request (after the 302), there is a difference… Is there something that i have done, or can do to prevent this behavior.

Original: Contact: <sip:44123456789@>

After Redirect: Contact: <sip:+44123456789@>

The Contact is supposed to be my fromuser so i can pick it up on the other side - but now it fails, as the + in front does not match the peer.

It appears to also happen with the From tag, tho this is not so problematic:

Original: From: "Bob Smith" <sip:44123456789@>;tag=as34e8f241

After Redirect: From: "Bob Smith" <sip:+44123456789@>;tag=as702ca351