Some voip carriers charge after the beep on early media (before the ANSWER), is possible to run the AMD() on the early media to detect this beep and hangup the call?
I think you are assuming that AMD is more sophisticated than it is. It doesn’t detect the presence of a pure tone, only a pattern of sound and silence.
Also the normal sequence for an answering machine is:
So you seem to be assuming strange answering machines. Playing the greeting as early media won’t work with the type of POTS line I’m used to.