Overcharging on contract

Around 4-5th of May my bill went up to R2000. This to me didn't make sense because there is no ways I can use so much data within such a short time. I do receive sms telling me the status of my data bundles and I buy data bundles when they are close to running out. At the current moment my bill is R3000 and I can clearly say I am not happy with this amount.