refusal of contract cancellation

i had it with mtn.<br> i wanted to cancel my contract, i went in may and it had to end the 4th of july.<br> i was told if i wanted to cancel i had to pay an extra R900.<br> <br> so i was stuck with a broken phone that i had to pay.<br> <br> now my contract had to end the 4th of July.<br> but it still went on. they refuse to cancel because i owe for my august airtime and BIS.<br> i did not even authorize or sign for it to go on. I signed til 4th of July 2015.<br> and it wont be cancelled so i will sit with further charges. that i did mot ask for.