MTN REFUSING TO LET ME GO OFF MY CONTRACT.

So my 24 month contract with mtn has ended and they ask that you give them cancellation notice a month in advance. I have been trying to do so I don't know for how long. When you call they say just coz your contract started on the 9th you need to give notice on the 10th. The 10th is a public holiday so when should i serve notice. They say no serve notice on the 13th which also a holiday.. The chances are of I call them on the 14th they will tell me the debit order has been run and it can't be reversed. I mean you have been paid in full what is so difficult with letting a client go off contract. We don't enjoy coming to report you guys here it's a waste of my time. But I dont want my contract to continue after my last payment why should I make sure i cancel it on the exact same day I took it? I want out of the contract