MTN BIGGEST BUNCH OF ******S AND *******

I took 3 mtn contracts on Black Friday 2 years ago. the contracts gave me lots of bonus data. we were due for upgrade in November this year and were waiting for Black Friday specials. I nearly had a heart attack when I received my mtn bill this month. I was charged R2229,21 for my personal account which has been around R500 for the past 2 years and R3731 for my 2 kids accounts which were R299 per month for the past 2 years. I was told that I am now being billed for all the bonus data because my contract expired!!!! this is ridiculous!!!!! why was I given the bonus data if my contract had lapsed???? this is ****************. I now have to pay R6000 . i refuse and want this reversed. I havent even used the bonus data-mtn can take it back. i really hate MTN and their Mafia tactics