MTN contract

MTN suspend my account every 2 weeks even when my contract has been paid. I was paying R275 and suddenly they debited R520 and I reversed it and asked what is it for? They never answered me but they told me they investigating it so I should pay R275 until the issue has been resolved. Immediately after the call, they sent me an email about payment plan that says I agreed to pay R1480 for 3 months and when I ask they says I should ignore it and pay the amount we agreed about. I paid all the monies that they said I'm owing and they still suspended my account for August payment and it's mid July. I have been paying for service that I don't even use😡😡😡 since April. I went to MTN stores and I have been calling but they still can't resolve the issue.