Battery life in my Xperia XZ1

Good day to you all my friends,

I have my XZ1 since last January, and i confirm it is a great device...

before a week, i used the mobile to take videos in the Red sea. since that time i noticed that there is a problem in the microphone as there is a noise and the other part cannot hear my voice. and the battery life indication was something weird.. it showed a 250 days to empty...

I sent the phone to the service to fix the microphone issue, after three days of waiting, they re installed the latest version of Android and informed me that there is something wrong within the board and it is expensive to fix, rather than there is no spare parts.

i took the phone, inserted my SIM and switched on, it seems that the microphone issue is fixed.. but the battery issue is still...

with 80%, there is two days and 3 hours remaining to empty..

Can anyone help?