Overcharged on fnb connect sim

So we did a online simcard contract for R99.00 a month and we receive a shocking invoice of R1300. How the hell is this possible. The invoice doesn't even show how much data we used and the first 2gig is suppose to be included in our premium and we just used over 2gig. You are ********ting us and now i tried phoning your call centre only to be on hold for 15min. Still no answer. This is unacceptable. So where are we supposed to get this money? Nowhere did you state this this is an 'open' contract. We signed a contract for R99.00. And there's also service fees on the first invoice that's not on the second. If I dont' get any proof of the data we used I will reverse the debitorder and cancel both contracts we took since that contract is void. You are lying about the contract and thus *****ing our hard earned money!!!!!