Nokia India — service center damaged my phone

Address:

Udaipur, Rajasthan, 313001

I have submitted my phone to nokia care udaipur rajasthan having touch issues on 23 april 2019. They opened the device and checked it then created the jobsheet. After that, they told me that it will take up to 15 days so i picked up my phone from them because i have to leave for gandhinagar. At gandhinagar gujrat nokia care on 27 april 2019, the person again opened my phone, checkedand told me that 4 screws are missing,, the antenna is damaged in the inner side and a small dent is on the other side of the phone and refused to repair it in warranty.
I have called nokia care helpline but they are blaming me that i have opened it and made the damage. My phone is in warranty period then why would i have opened it?. I can not see inside my phone to see screws missing and damages made by your service center
My imei number is [protected]