Disappointed in MTN South Africa

So disappointed in MTN my phone contract is coming to an end and on my last invoice they charged me for international calls and sms of which I do not know off. I asked the agent to give me the number I made an international call to and they fail since I cancelled my contract. Told them to cancel everything and close the SIM card yet I got an sms saying i am on prepaid and will be paying R300 something while I made it clear they can close the SIM card as I have no use for it.

I have been using this network for years but now I have to stop using it