[Freeswitch-dev] Connect Voice mail flow before sending Answer.

Hi all, I am new to Freeswitch & need to do following. When called party not available, I need to route call to voice mail system without sending answer.(or OK) If send answer, calling party will be charged. So I need to avoid that. After that I need to prompt message as "Press 1 for go to voicemail or Press 2 to exit" If user press1 then send answer (Charging is start) & connect to voice mail call flow. For doing above, shall I need to do code level changes ?? Pls advice. Br, Sanath