heat on phone is getting up while charging and during video call

It’s normal for any phone to get warm while charging or being used. The phone has over-temperature protection, and if the internal temperature gets to high the phone will shut down and display a message saying it has to cool off. If this isn’t happening then the phone is working correctly.

Charging, phone calls, and video are the heaviest users of energy in the phone, and if you are doing all of them together it can make the phone very warm. For phone calls and mobile data the strength of the mobile signal has the most affect. If the signal is weak the phone must increase its transmitter power to maintain a connection. A 1 bar signal uses 10 times as much energy as a 5 bar signal.

Does it say that it has to shut down? And please be clear. If you had said that originally I would have answered differently. If it is too hot to touch contact Apple Support using the link at the top of this page.