Unacceptable service

I got a laptop and data contract with Autopage, service was good, however the sales person forgot to give me vital information, where he had to inform me that as soon as my 2GB data was finish, i would get billed extra after the 2GB was used, and because of this vital information not being explained to me i recieved a bill of over R4000 and if he had told me that this could happen i wouldve been more carefull!!!!!!