Unsatisfied customer

I regret getting into contract with MTN, I had a rooter contract with them for 24 months, they used to debit R250, this month was my last month of the contract they debited R600, I went to the nearest mtn customer service, I was told i have to upgrade or cancel the contract whereas the contract was for 24 months and it's past that, no one notified me about that I just saw a debit order of 600 in this difficult time when I asked one of their employees to cancel she told me I need to contact another department which I also can't get hold of them so this is a ******** act and I'm very upset I would advise people not to use mtn even their data is very expensive.