[Freeswitch-users] Using session.getVariable with start_stamp, answer_stamp and nibble_total_billed return empty

Hi, I need to call some web API after the call finish with parameter answered time stamp and nibble_total_billed. I am using Javascript session.getVariable to get those parameters, but the start_stamp, answer_stamp, start_epoch and nibble_total_billed returned empty. How to get the start_stamp, answer_stamp and nibble_total_billed in Javascript scripts? Donny