Yes, the trunk group is pointed towards the CRT. I have the E and the + at the end. I do not have inbound authentication disabled. I tried enabling it to see if there was a miracle, but it did not work. I tried using the last 4 digits. The Numbers are at the top of the CRT. I contacted Flowroute and this is what they said..I am not sure what to tell, your system is rejecting it, given the 403. Most often this is because the SIP Server IP or FQDN is not listed as PEER, inbound authentication is turned on, etc. I am pasting the two invites below for your consideration, as I am not to familiar with the MITEL 5000 and maybe it is blocking the call based on the Contact Header.
1-877 contact Contact: <sip:wlssuser@23.29.25.120:5060;sipappsessionid=app-uv7ef9sraytm;wlssfcid=sip-1xhb1vw736smn>
locall number Contact Contact: <sip:+1715XXXXXXX@74.XXX.XXX.XXX:5060>