Lenovo — lenovo vibe x3 mobile-apps permission issue not resolved even after 20 days

Address:

Chandigarh, Chandigarh, 160047

I am writing this after being totally dissatisfied, annoyed & disenchanted with lenovo mobile service center in chandigarh-sant rameshwari enterprises. I was facing a software problem (Apps permission issue) & gave my lenovo vibe x3 mobile to the service centre on 20th july’17 but they could not resolve it. After numerous visits & a hundred calls i was forced to take back my mobile from them after 20 days on aug 8th’17. As per them they have not been able to understand & diagnose the problem till now after downloading new software 2-3 times.
Now the problem.
I am not able to access my contacts, make calls, see videos or access some of the apps on the mobile as it is not giving permission (Apps permission issue) to access. The particular programme/app is first saying:
“one or more permissions need to be set on manually in settings if you want to use this application”.
Then on pressing the setting button & accessing the app permissions it is showing:
“screen overlay detected”
“to change this permission setting, you first have to turn of the screen overlay from settings apps”
Thereafter it is not giving permission.
Please help.