Disfunctional Samsung Tablet 10.1

Good morning<br> <br> I purchased a Samsung tablet 10.1 from the MTN store in Rosebank in December 2014. A few months down the line, the device started giving me problems, it did not want to charge at all so I took it to MTN service centre in Morningside Rivonia road for assistance with repairs. My phone returned and it seemed to be functioning fine. Its been months again since the repairs, and the phone is giving me problems again. It started with the charging, I switched off my phone to charge it overnight and when I woke up to switch it on, it was still on 30%, after over 4hours of charging, when it switched off when the battery was drained, I put it the charger but it would not charge. My phone has never fell or been in contact with water. I pay instalments every month for this device. How many times do you need to send in a phone for repairs before the company see's that there is a fault with it. I do not have time to keep travelling to mtn for repairs for the same problems. I have important emails that need to be checked on the regular. I cannot afford to purchase another phone while still paying for a dysfunctional one, PLEASE ASSIST URGENTLY