Disable Disconnect feature in Asterisk

Hi ,
The agent is logged in the queue . the caller makes the call ,goes to the queue and agents pick the call . How to disable the disconnect feature through DTMF for agent in asterisk .

exten => 1234,1,Queue(Test,t)



[quote]; Define endcall to allow an agent to hangup a call with a
; DTMF keypress. Default is “yes”. Use the enddtmf option to
; configure which DTMF key will end a call. The default is
; '’.