Incorrect billing

My account has been debited with R2930 this morning with consultant unable to explain further. I recently upgraded my package to a total of R549 and a further limit of R500 extra airtime value. I however did not go over my limit yet it was said that I had used over R2000. It's impossible because I recharge with data and am notified when it has completed and then recharge again. Same with airtime value. <br> This is unacceptable and I refuse to go on further with this service provider as a similar incident has happened two years ago