Inferior Tablet

I purchased a 50th birthday present in the form in the form of a tablet at Ackermans. The first model I had to return refusing to work from the start. They exchange it for the model on special with the condition that if the model give problems it needs to be returned in 7 days. The model give problem on day 8 by deleting everything in memory. I was told it is because the sim card is full. I had to explain that the Tablet has it's own memory. They spent several ours with Cell C just to realize it is not a Sim problem. They exchange cards and assure as after several visits of at least 3 hours each that the problem is sorted out, otherwise we can leave the tablet for four weeks so they can send it in for repairs. This deal was done in cash from the start, the recipient of the birthday present did not have a working tablet from the start. They did not wait for their payment, why do I need to wait for a working tablet bought as new?