Why do my calls get cut off automatically after some time ?

Can you give us more details as to what conditions exist when this happens? Does your call always drop after the same amount of time? Are you moving, or staying in the same place when this happens? How much signal is your phone showing on the indicator when this happens? Does the phone and/or battery feel hot? Do you have to turn the phone off, then on again to make another call?

 

Hmmm. I used to have this happen to me when I had the ancient AT&T Wireless Go Phone plan. After 3 hours of continuous talk, the phone would automatically disconnect. I assumed it was a plan thing since this happened to me on different phones.

I have talked on my Verizon phone for 5+ hours without a disconnect.

Sent from my DROID RAZR using Tapatalk 2

 

Here in Turkiye, the calls were cut off after two hours of talking. If you want to talk more you need to call again, or the other side has to call. This is some kind of precaution in case call is done unintentionally, so that customer doesn't have to pay bills comprising of lots of zeros, or to stop minutes in the plan gets exhausted.
Some users with limitless talking plans use 20 thousans minutes monthly, they aim to stop this users as they probably keep their phones connected even when sleeping. Also these users cause continuous load on the network that can prevent new calls from being established. Thus in some way, operators doesn't want continuous calls on their network.
Better solution can be Skype and other VoIP options. They cut off the call, but not the internet connection.