Recurring payment

Good day

They keep on debiting on my account. Around 2014 I bought phones with MTN and later on I couldn't pay and I sent them an email asking them to cancel my contract but they didn't respond to my email and when I called them I was told that I was handed over to their legal team. The legal team called me and I told them that they can debit every month until I'm done with my account which was supposed to end of September and when I called them they told me that everytime I call they charge me.how is that even possible I'm the one keeping tabs on my account since they don't send any statements. So I want to show people that this legal team of MTN is reaping people off their hard earned work money.