Here’s what we want to happen:
A user calls our DID # … the call is routed to our Asterisk box … the user enters an extension (for instance, 1000) … Asterisk dials a pre-defined PSTN # … if the line picks up, Asterisk connects the incoming call with its just dialed outbound call … if the outbound call does not pick up, Asterisk drops the caller into the voicemail for extension 1000 …
Also, we are using AMP … but can manually edit the config files if necessary … our VoIP provider handles all origination/termination services and uses both IAX and SIP …