Xiaomi India — battery draining issue

Address:

New Delhi, Delhi, 110005

Sir i am getting battery draining problem in my phone..
When phone battery is 20% phone gets switched off. Phone battery is draining 60% to 35 % in few minutes.
When i visited mi care shadipur they are saying that this is a software problem. And they updated the phone software.
But nothing happened.
When i visited again and request them to change the battery because phone is in warrenty they are saying that we can't change the battery because your phone is okay.
But i know the phone battery is not okay it draining very faster.
But they are not listing to me at all!
I suggest mi phones to everyone.
But after this experience i don't even think to purchase mi phones.
Phone model : redmi 5a
Job sheet attached.