Data usage - Ridicilous account

A month ago I contacted Cell C to enquire about their 20gig (5 day/15 night) Huawei portable wi-fi contract for the amount of R269 per month.For only one person using the data this contract was more than enough, not even thinking that it was possible to exceed 5 gig let alone 20gig.Three weeks into the first month, the line was softlocked.When calling Cell C they informed me that I have exceeded my limit of R2000.Firstly,where did the R2000 limit come from,who approved that amount,(as far as I understand my only amount payable was the contracted amount of R269),and what happened to the 20gig data?The call centre gent explained to me that the device was used to download data,(with a daughter at university using this devise, how is it possible to not download stuff) - and with this contract only browsing was allowed.Now please assist me?If the sales consultant did not explain to me that I am only allowed to browse, did not confirm that this is an open line and confirmed that I have a 'limit' of R2000, is this not then misrepresentation. I will apologise profusely if he in fact did mention the above when he sold the contract to me and I did not listen properly.