Install and modify asterisk call billing software.
Billing software should do the following:
When callers dial in, they are prompted to enter PIN.
Software announces how much money they have in PIN
Callers are then prompted to press 1 for group A and or two for group B
When callers reach each group, they are prompted to press 1 to enter a specific ext for a person in the group or press two to dial everyone in the group.
Asterisk then dials out.
Call recipient picks up phone and hears voice file saying press 1 to connect.
Billing starts only when call recipient has pressed one to accept call.
Calls must never go to recipient's voicemail.
Per minute charges for group A and group B should be changeable.
Call recipients in each group could be able to log in/out when they want to accept calls.
This will be on Tribox [url removed, login to view]
Feel free to use PMB for suggestions and questions.