MTN ARE USELESS

I took out a tablet contract for my daughter in March 2015. When they checked my bank details they had my old Nedbank account. I told them that this was closed but I could give them my FNB details. I was told no don't worry its not a problem. WELL it is a problem because now the debit order isn't coming off my account. I went into the Stoneridge branch on the 15th May to get a balance and pay my account. I did a transfer for the amount they required and was told that at the end of May the debit order would come off. Well guess what it didn't. I haven't had another statement and when I went to MTN Karaglen I was told that R288.74 was outstanding and that was the amount I had paid on the 15th May. I asked what else I had to pay and was told nothing they would sort it out for me. Today I get a threatening letter from MTN asking for payment in 14 days otherwise they will take legal action. I am absolutely astounding that this **** is happening. If the sales person at MTN Greenstone had of just changed my bank details when I asked them to I wouldn't be having this trouble. Are MTN just in for a quick sale and no after sales service. OOPS I forgot they don't understand the word service