Samsung India — motherboard damaged by samsung service center

I had a display break down. I gave the phone A9 pro SM-A9100 for repair . When I submitted the phone the display was half working. He quoted me 5900/- for the same. I submitted on 21.09.2019 (FRIDAY)and they told me that I will get the same on Monday i.e on 23.09.2019. But it kept delaying and finally they said they have got the display part on 25.09.2019. When I submitted the phone the customer service executive did not check my phone. Later when I went to receive my phone, he said there is a problem in the motherboard as there is water in it which is dried up and that is why the home key and back key is not working. I asked him how can I trust that my motherboard was not damaged by Samsung and it was already damaged. The customer care executive told me that he will give me the full CCTV footage of 4 days of how the phone was handled. I agreed. AS SOON I AGREED, THE OWNER OF THE SAMSUNG SERVICE CENTER, DENIED AND SAID I SHOULD FILE A LEGAL CASE . I WILL SUBMIT ONLY TO COURT AND NOT YOU. I then asked him how is it possible that when I gave the phone that time the display was half working. If motherboard Is damaged, the phone will not work at all. He says we come to know when it was opened. Now how can I trust him that he did not do it and it was already damaged. He quoted me 7000/- more that comes to total of 13000/- he is not given me CCTV nor any evidence that it was not damaged by them. Please help at the earliest. It's very serious . We don't pay high prices compared to other phones for such negligent services.
Please provide me with the resolution at
[protected]@gmail.com