Screen replaced, got given the wrong phone

I picked up my phone after many problems.<br> I think during this my phone may have been lost because now that i have powered my phone, it is completely different.<br> Not only is this a different OS version, but ALL of my memory is gone. 25 gigs of personal data is gone. Irreplacable photos and videos, including the only copies of my sisters birth, completely gone.<br> <br> All i want are my files back. I payed to have a simple screen replacement. I did not pay for this <br> I want my files back or i want a partial refund. I did not pay to have my OS replaced and my files deleted.<br> And i honestly believe this is a different phone. I will check my serial number when I get home.<br> <br> MTN please just give me my files back. Thats all i want. I cant replace the files I lost and I am extremely distressed at losing them