I came back to Asterisk this week after a few months abscence.
I was trying to set up outbound calls through the SIP service provided by voipuser.org.
The issue I had was I added a context into Extensions.conf using a #include and a patern of _9. for 'dial 9 for an outside number' but although I could see this on the dialplan, it was never matched and therfore my outbound calls were not getting out.
After a number of hours of tracing it appears the issue is with the way that this assistant is creating the sip files for each extension.
The genrated SIP file includes the context directive and set this to autocontext. Since the context directive defines the context for outgoing calls on a channel, this basically appears to mean that the only outbound calls that can be made form these extensions is to any of the other extension created with the assistants, and to anything within the demo context, which appears to be included in the autocontext.conf.
My temporary fix is to add my include to the autocontext.conf file. Hoever this is probably not ideal since this file is system generated.