I do not think you need a suffix on this "sip.tollfreegateway.com"
I think instead you need to set up sip.tollfreegateway.com as a VSP
then conform your dialing plan to theirs, and send the call to that new trunk
probably what is happening from what I understand you are probably sending out a call like
Code:
1800XXXXXXXXXX@sip.tollfreegateway.com@sip.otherprovider.com
but I am just guessing.
The easiest way is actually just prepend the 1800, 1877, 1866, 1888 numbers with * and let voxalot handle them, as if you dialed them with the *.