MTN repairs are useless

My htc one m9 was booked in in march where they had to replace the board. after receiving it back the phone 's screen became non responsive in the top right corner. They replaced the screen but the problem still persisted and i'm not talking that the screen has a new problem its the exact same area on the screen. So it was booked in again and had to wait two and a half months to get it back where I was told again they replaced the screen. Guess what the screen did the exact same thing again and was booked in again. Now they tell me there's mechanical damage and that's what causes the issue. So My first problem is if that is the cause of the problem why wasn't it detected the first two times, my second problem is that I have effectively been without a phone since march as its been booked in almost constantly and now for the last 3 weeks I've been given a different excuse on a daily basis as to whats going on from the repair center.