HTC India — htc desire 728 mobile brightness problem

Sir i brought htc desire 728 d728w from store at 27/12/2017. I got a problem of low brightness. Then gave it for repair to preet services, 9-b, arpa complex, bilaspur, chhattisgarah at 14/08/2017. Today i got inform that my have mother problem and it need for repairing charge of rs14000 approx. But my mobile is in under warranty. Then i called to custmer care no-[protected] and they told same think and gave the ticket no-[protected] and told me disassembled at out side of service center. So charging is needed. But it is false story about disassembled. I am getting first time problem.
There-fore i request to u sir please solve my problem as fast as possible.