Iphone 12 heating up

Hi

i have been using IPhone 12 for past six months but i have been experiencing heating issues from the

very beginning. I have got it checked at Apple store once but to no avail, the executives said the phone is fine but they did not have an answer for heating up. Again an executive carried out diagnostic tests remotely but no use.

Normally phone heats up while:-

1. using the hotspot.
2. making a video call on whatsapp/line even for 10-15 mins.
3. sometimes while charging.