SoftHangup( ) Performs a soft hangup of the requested channel
SoftHangup(technology/resource,options)
Hangs up the requested channel. Always returns 0. The options argument may contain the letter a, which causes all channels on the specified device to be hung up. Currently, the options argument may contain only one letter: a. Supplying the a argument causes all channels on the specified device to be hung up.
; hang up all calls using Zap/4 so we can use it
exten => 123,1,SoftHangup(Zap/4,a)
exten => 123,2,Wait(2)
exten => 123,3,Dial(Zap/4/5551212)