Hi
As the balance is updated at the end of a call, there is little to be done about this.
There are measures to alleviate the problem:-
1. Make use of Reserve Balance in the AGI-Conf, this will remove some balance every time a call is made, and put it back at the end of the call.
2. Consider using
http://www.asterisk2billing.org/add-ons ... ls-module/ to limit the number of concurrent calls.
With some development time, we could probably extend this dial-plan to actually cut off every call for a single customer when one call hangs up and the balance <= 0
Joe