Setting up an existing and working EXTERNAL SIP account as Trunk in Freepbx

Please read careful before replying: Case: - Existing Freepbx; up and running! - Existing SIP account successfully registered on MicroSIP application on Windows machine; thus the SIP account works 100% fine using MicroSIP. > By this I mean: I received SIP information from my phone company. Using this SIP information I can place outgoing and incoming calls using MicroSip. - The SIP account is NOT blocked anyhow (like certain domains or whatever) - SIP account contains an “@ sign” in the username - SIP account needs to registered using UDP only I'm looking for a fixed price. Installation of the SIP account as trunk in my freepbx should be done via remote desktop (teamviewer) Note: I’m NOT asking to install a trunk, just a working SIP account in the “trunk section” of my freepbx, so that my extentions (using the outgoing route) can use this SIP account as outgoing line. You can copy the information I have entered in MicroSip 1-on-1. My problem: I don’t know how to handle the @ sign in the username AND to set UDP only. Thanks upfront for your reply!