I was given the following credentials for my SIP account which I plan to use with my 3CX Phone System: Line number: XXX Auth ID: YYY Auth pw: ZZZ For the line to work, my provider requires the "Contact", "From", and "To" SIP headers to use XXX as the user part. YYY is only used during authentication digest. However, 3CX sends "YYY" for all the "Contact", "From" and "To" fields during SIP REGISTRATION. And I don't seem to be able to change that at all. I am currently using v9 RC1 (9.13373). SIP INVITE fields are changeable under the Outgoing tab, which I did. I sniffed the SIP packets during an outgoing call which seems to be correct. However, my provider does not allow making a call without a successful SIP registration -- which means I am stuck until I can customize the fields for registration. Please help!