Xiaomi India — mi note 6 pro handset

Address:

Village and Post - Sikhera, District - Bulandshahr, Uttar Pradesh, india, Bulandshahr, Uttar Pradesh, 203002

I brought a new handset of Mi note 6 Pro in the date of 10/02/2019. But after some days my phone start screen billing after running 15 to 25 minutes. Then went service centre of Mi in bulandshahr. But there my problem not solved and my handset also damaged from backside by service centre workers.
Please give me the solution. What will I do?