I have been testing out the Grandstream UCM6102 PBX which uses asterisk. I had a problem with 3 Voipo accounts set as trunks, where everything is the same except username and password for each trunk. So it wouldn't let me do the inbound routes right. What would happen is, all calls for the 3 numbers (trunks) would go to what the first route was set to. So then i found out if i set the 'DID Pattern' to _2065551212 (user name of trunk) then the inbound routes would work for all 3 trunks.

I don't know if this helps you as the Grandstream has it own custom GUI.