Best way to set up this trunk?

I have purchased an IAX2 trunk from a local provider for incoming and outgoing calls to the pstn . He appears to have good intentions, but normally doesn’t sell IAX2 trunks on their own, so we’ve been having troubles getting this right. I have purchased 604-123-4567 from him for use with this.

Outgoing calls from my SIP phones work without issue.
Incoming calls however do not work as expected. I was told to use the following settings for the INCOMING trunk:


I was told that the REGISTER string was not needed, so it is blank.

Regardless, with this setup, and incoming calls to 604-123-4567 just get a busy signal.

A stopgap solution that we found was to set up an extension (250) for the provider. He in turn takes the incoming calls to this extension, and forwards them all to extension 200 (which is local to my network).

This works and all, but I can’t find a way to get either caller ID to work (all calls say they are from Ext 250), as well as things like an auto-attendant.

Does anyone have any suggestions as to what I should do to get this working well? I am using Asterisk@Home on my end.