No limit was set on the account

On the 4 August 2016 my wife took out a new contract at mtn 0235 vangate mall.She sign up for a 500 mb data with a Wi-Fi route and a 55 Samsung TV for R749 a month. In September her bill went off right in October the problems start with the debt order we went to vangate mall mtn and spoke to the guy who did help us and he told us it was a system problem,because she never sign for open line of R1000 we went several times back to the store and he told us he will sort it out,and nothing happen we also spoke to management of the store and they refuse to help us.We contact 808 and explain the story to them and all reference numbers we received from them say the store must sort out the account.She have 2 accounts with them in June they start putting off the phones but when she phone 808 they put on the phones again just for few days then the phones go off again ,but every month my wife pays the account.In December 2016 she phone 808 and they put a limit on the account and one of the USD numbers shows that he never put a limit on the account. It is a year know we struggling with this account with mtn.We pay the account but we cannot use our phones because of the problem with mtn.I think is so unfair!!!!!