False deductions from my account not being rectified in spite of months of calls and emails

I have a limited data contract with Vodacom. Every month R235 was deducted from my bank account. Then all of a sudden They deducted R5000 and R8000 etc for three months when I stopped the debit order with my bank. The bank refunded me 2 months, after which I was told by Vodacom I was in arrears. The first month of aver R5000 I did not get back. I have been contacting Vodacom for months with numerous phone calls trying to get them to sort this out. All I am getting is threats to take me to court. How can a limited data contract suddenly jump to those amounts? They are not rectifying the problem and I do not know what to do any more. I would say, avoid this company. They are not reliable and they appear to cheat people out of money.