*********** repairs

I have had a new sony z3 compact tablet for 2months and have booked it into the repair centre for more than six weeks. Thus, i am paying for a contract that i am yet to enjoy the benefits of. I booked my tablet into the repairs with a blotch on the screen, it has been returned to me twice claiming that no fault was found but the blotch is still visible. I booked it in for a third time yesterday with the same problem. Currently i am paying for lost data and a device i don't have. I have pointed out the mark to the consultants at the centre and they have seen it, but the engineers are blind. This is annoying and i am frustrated with the service. I would prefer to cancel or move my contract to better service provider or receive a new device.