[Asterisk-Users] double-dial in SIP Grandstream

[Bisker, Scott (7805)]

Marc,

This is the typical behavior for call waiting.  While you are initiating a
call, people who call your number will get a busy signal until your first
call connects.  Once the call connects, the number 2 caller will hear a ring
until you pickup.  

If you want to disable callwaiting then put "callwaiting=no" in sip.conf for
that particular alias.

[<alias>]