Mtn ****

My Mom went to Mtn in Westgate mall to get a router on contract, she was assisted by the lady called Kgomotso. She was advised that she must pay R150 for the simcard upfront which she did but was not issued with the slip. She was told the first installment will be R560 or so then only to find out that she's supposed to pay just over R700. I would like to know how did it come up to almost a thousand Rand. Is Mtn ******** my Mom