You can see with the current call reports/call logs page
number of calls per extension, and in call logs you can also see the specific calls that a specific extension made... Please have in mind that there was a small bug found in the reports section of the software were calls are reported to 1 gateway only instead of normally reported that they are all made from different extensions. Please check this issue aswell because we haven't had time to fully investigate this to see if this somehow affects also the extensions reporting....