я конечно могу ошибаться, но
options
A(x):
x - The file to play to the called party
Play an announcement to the called party, where <x> is the prompt to be played
a: Immediately answer the calling channel when the called channel answers in all cases. Normally, the calling channel is answered when the called channel answers, but when options such as 'A()' and 'M()' are used, the calling channel is not answered until all actions on the called channel (such as playing an announcement) are completed. This option can be used to answer the calling channel before doing anything on the called channel. You will rarely need to use this option, the default behavior is adequate in most cases.
вроде оно как раз для этого