Unbelievable bad service from Apple South Africa and iStore Cavendish Square

My iMac I purchased at this store after 15 months no longer powers up. I call Apple support, they try to assess the problem and tell me to take it in to nearest servicer, they direct me to webstie where I can find the nearest, it turns out to e iStore Cavendish square where I bought the iMac, they DO NOT TELL ME I NEED TO MAKE AN APPOINTMENT FIRST. I arrive with the iMax in its huge box in a shopping cart around 12:00 on Monday, I have a meeting at 13:00 so it is a rush. Although there is almost no-one in the store they refuse to take it and insist I make an appointment, I make appointment for 15:30, I have to haul this huge box back to my car, pay for the parking, rush for my meeting, miss lunch then after meeting rush back to this store, haul the huge box out of my car again, pay for parking again, and then wait in line ANYWAY!!!! at the store to be helped. At last they check the iMac in. Now Friday and not a word of feedback from them, I call the number on the "Repair Acceptance Letter" they made me sign 3 copies of, and the number takes me to Nintendo customer service, I cannot contact these people with my iMac.