charge level drops faster than normal

Hello guys..

so I took my phone to a local technician. He claimed that the battery needs to be replaced, he replaced it and I took the phone home, I exported the contacts from the phone.

I charged the phone almost fully, but in the morning the phone was OFF and I couldn't do anything with it, even though I plugged it to the charger for one hour nothing appeared on the screen!!.

I got back to the technician. He claimed that there's an IC that consumes power even though that the phone is not in use!!!?. He was able to turn it ON, and he proposed that I don't let the phone charging level drop to 0%, cuz I have to visit him back to make it work back. But the problem is that the charge level drops faster than normal.

He refused to replace the IC, and claimed that the board will never work again!!!!!?. Have you heard of such a thing guys, I don't believe that at all?

How the technician gets the phone back to work, while I can't?, does he supply it with a higher ampere level?, If so, how much?

What do you propose guys:

1. Ship it to a company where they can replace this IC? If so, where? And how much the expected cost?

2. Buy a new main board, if so, from where (it must be unlocked)? I noticed that the board cost too much - about 150USD exclude shipping and customs