OnePlus India — oneplus 6 mobile battery backup issue

Website:

Oneplus care servify

I bought oneplus 6 mobile on may 23rd and initial performance and battery backup was too good. All of a sudden am facing few issues.
1. Battery backup comes down from 2 days to less than a day.
2. Performance is slow
3. Camera am getting unknown error

Then i registered a complaint through on plus care app and selected battery backup issue. The pickup was scheduled on 27th october.

I have wiped my data and app as per instruction given. But one week later i called them again since there is no clue or update and got to know the poor service that still they haven't received.

Finally they received and marked it as software upgrade done, ready to dispatch. I called them and updated that the issue is with battery not with software. They replied i should not have deleted or resetted if there is battery backup issue. I asked then to diagnose on the battery and that service center num is not readable for last four days. Response was pathetic. To diagnosed 12 days is too much, with no repair done. Pathetic support.