Unhappy with Ackerman's Cell

Yesterday I bought a Tablet at Ackerman's cell in Chris' Hani,wanted to use for business and educational purposes but unfortunately when I got home I found it to be non responsive when Searching plus it's reaction time was frustrating,so today tried to exchange it for a better one even if it means payinf more but I was told I can't as it was technically okay for them even though they saw it was slow and it's screen response when pressing was not good and I was turned away to my disgustment.