Hittting the Corporate wall

I signed up for the R199,00 data package to receive 5 G day and 15 G night time data. My subscription was for only 199 ,00. I took out the contract as it seemed affordable. I was charged in the excess of 2500 ZAR and when I called customer services they passed me to the branch where I signed up. I was never informed that I had an open line?? Needless to say I will be hit again by a corporate wall where I will be bul****. Please assist.