Unhappy with service delivery

I bought a Samsung tablet at one of your outlets in Rustenburg, North West, about a year later the tablet gave me problems. I took it to the MTN for repairs knowing that it was still under warranty, I later got an sms saying I should pay R1450 for repairs. So I waited a few days to think this through then I got another sms saying I should pay roughly R4500 which didn't make sense because the tablet its self cost less than that at that time. So for roughly a whole year I paid for a device that WASN'T working and that really ****ed me off. I later took my tablet back to MTN and they told me that my tablet was no longer under warranty, I tried too explain to the person whom gave me services that I had came earlier and the response was that she can't do anything about it, it was out of her hands.