Default Call drop problem on CM11

hi everyone

My calls keep getting disconnected after 2 or 3 minutes of talk.
I tried changing the radio and it didn't work, i also searched the forum with no avail.

Any help would be appreciated
Many thanks

Click image for larger version

Name:	uploadfromtaptalk1388426265891.jpg
Views:	452
Size:	66.4 KB
ID:	2483877