cancel my contract

i had a sim only home data with man, contract ended last month.i gave me new offers which i was not happy with..i was then told that my subscription will now be a month to month..i did not pay last month and did not receive data which is reasonable..to my surprise i received a call yesterday saying i owe man R1200..my contract was for R210,how did we get there when i have never received data andnwas advised the amount wont change..all i want is for my contract to be canceled.