MTN subscription from hell

I have reached the boiling point trying to cancel a mere R210 data subscription that has now turned into a nightmare! I tried over 10 times through the past 2 months to cancel this contract and every time I either get put through to wait for an hour on the line or I get told my request has been sent but I don't hear anything after that. I have emailed them with no avail, I have even sent twitter messages over and over again and have been told my request has been sent. On top of all of this, I have expressed multiple times that I am not currently in South Africa and cannot be contacted when they say their retentions team will call me back. How hard can it be to cancel a damn data contract? Instead I have had two debits for over R500 which are not even the agreed-upon amounts for the contract. MTN reverse those debit orders and cancel my contract!!!! Worst service EVER!!!