Redmi 5a Grey - mobile warranty rejected

dear sir, my redmi*a mobile under warranty period, suddenly found network issue,my phone show to service center mangalore on **th june **** at around **:** hours they opened phone inside and told no warranty due to outside tampered, screw missing and LCM strip damaged. its not possible because myself used mobile never opend mobile, so am asked you give writtenly they refused, finaly they told pay *** rupees and get writtenly , i agrred, they print the job sheet again they took mobile inside after ** minutes they give service record and mobile, iam understand they first warranty rejected after they create evidence, i called custemer care, and sent mail, nothing they do needful, service record no WXIN*************