billing for data not used

I had a MTN data contract with 2GB data per month for the past three years. I never used more than the 2GB data per month during the past three years. For the period June to Aug 2015 I received accounts for the tatol of R8042-52 for data used during this period. I tried on several occassions to solve this problem with MTN but without success. According to them Microsoft did a lot of updates and that is the reason for the high usage of data on my account. I got so frustrated wih MTN for paying for data that I did not use and their pathetic customer service that I terminated the contract.