Mtn debited more that what I signed for.

Mtn debited R209 instead of R199 from my account. I have a 24 month data contract with them, I was not stipulated that the amount was gonna increase and was not notified that they will increase the amount this month. I spoke to their service champion and she said I lot of contract client phoned in to complain but there is nothingbshe can do about it. I am not happy about Mtn at all.