MTN is a big time *******

MTN is a ****. My contract is ending this month and I called them and spoke to Sibusiso to cancel. He said the contract will be cancelled and I don’t have to pay anything as I had already been billed at the end of February however I will get my last data on the 12th. Now I am getting an invoice stating that I need to pay R1226 for 20gb that was loaded last month as the discount has fallen off as my contract has expired. From R229 how do they get to r1226? And why am I being billed when I cancelled the contract and I was told that I don’t need to pay anything else the contract has been cancelled?? How do you charge r1226 for data that I didn’t even request?how is 20gb r1226? MTN is a *****