Here is the exact path to find the hidden SIP settings in Symbian^3 v1.0 English firmware:
: To enable calling over cellular data instead of just Wi-Fi, you must use the SIP VoIP Settings app to toggle the "Allow VoIP over WCDMA" option to "ON". Codec Optimization sip voip 3 1 settings symbian 3 v1 0 en full
Under Registrar Server and Proxy Server : Here is the exact path to find the
Configuring SIP VoIP 3.1 on Symbian^3: The Ultimate Setup Guide sip voip 3 1 settings symbian 3 v1 0 en full