Horrific data charges on barely used contract

Activated my new contract of smart data 10g, pocket router on 23/10/2017 and on Thursday 26/10/217 i have been advised my account is sitting at R11275.16. i signed up a contract of R299 a month, how could i have possibly used all that data in 4 days, and just why was i supposed to have set a limit apparently on this account when i signed up for R299.00, i was never once told that i was going to have an open line. as per my understanding if i am buying something at R299, thats what i should pay, Cell C, is a bunch of *******, i do not have the funds to pay an account of this nature. I have always heard stories of cellc and their useless pathetic underlying selling tactics.