Lenovo — bad service by authorised service center and rude behaviour

I had baught lenavo zuk z1 in may 2016 and after 4 month there is a problem of auto reboot but at that time it occurs less no of time but now it reboots after every phone call 10 to 12 times in a day, so i submitted my phone in lenavo service center, kotla market, new delhi and they said they will tell about the issue after diagnosing and today they said there is problem in its mother board and it will cost u 9500 rs since it is not in warranty so i said not to repair and return it back whent i received my phone i found that its finger print sensor is now not working actually it is not present in the phone now, so i told them about this but they said maybe it is like this earliar and behaved very unprofessionaly and in a very rude way.
So please look into this matter i m disheartened by the service and behaviour our employees.