[Serusers] Cisco 7905G sends wrong realm

Hi, I have a problem with the Cisco 7905G IP Phone. I can't set the digest realm in the phone. The phone always uses the proxy (ser) IP or Adress as realm! If the Phone tries to register with ser, ser denies the request, because there is no user in the database with the realm "@ser_ip_adress". The user in the database is "user@my_domain". Creating an additional user (user@ser_ip_adress) wouldn't be a problem, but that's not what I want, because I want users from multiple domains being able to register. I tried to set the login name to "user@my_domain" in the phone, but this stupid thing uses "user@my_domain@ser_ip_adress"..... I know that it's a problem of the phone, but maybe someone has a solution for this? Jan Jankowski