MTN are ******

I regret the day I took a rooter contract with MTN they have been debiting the amount that I did not sign for it according to my contract they suppose to debit R299 every month. January they took R389 February R489 now I just got notification that they took R503 how insane is this?MTN are ****** they ripping me off but I'm going to put end on this tomorrow!!!!!!!I am so fed up last year they did the exact thing that is happening now