All outgoing calls disconnects after 27 seconds

Hi all,

I am using a freepbx with 4 spa941 phones, spa400 for the incoming PSTN line.

The problem is when I make a call, it will disconnect after 27 seconds. On my side the call is like ongoing but, you hear nothing, other side call disconnected message appears…

Could someone help me going out of this trouble…

Thanks.

jake