Phone calls dropped after approximately 5 minutes into calls

Check these settings:

• Auto screen off during calls
• Power Button Ends Call

• Turn off Proximity Sensor

I'm thinking the Proximity Sensor just shuts the screen off when you are farther away or the screen timeout is ending the calls or you are pressing the power button to open the screen again and that is ending the call.

With the info you provided, one possibility is that the screen times out after five minutes, locking the phone, and thus ends the call. This shouldn't happen during a call, but go to your display settings and make sure your screen doesn't time out to see if this solves your problem. Again, it is unlikely this is the problem, but it is a possibility.