I took a contract for R199 with 1GiG of Data and I was promised that is locked at 1GiG now I am billed with R699

Greetings

In September I took a contract on Huawei P8 Lite for R199 getting 1GiG and I asked the sales agent Quinton Polman that is the data locked at 1GiG and he promised me that yes it is and when that data is finished then it will not go beyond that. Saturday the 25 November, I have received the sms about my account that I will be debited with R699 and R499 is for data that I have used. I phoned the call centre immediately and I talked to a call centre agent by the name of Palesa and she said Quinton Polman was supposed to make me aware of other details about this offer. I said anything about the offer is supposed to be written on the contract and not be verbally communicated. I have tried to get hols of Quinton Polman on Saturday he 25, November at ********** /01 but I still could not get hold of him then I sent an email but I didn't get any response. Yesterday I went to the Telkom Direct Stellenbosch to talk to Quinton about this but he was not working yesterday then I talked to an agent by the name of Malik and he logged a case about this situation. What I asked Malik and the call centre agent is, the other data that I'm entitled to use for whatsapp, bbm etc how are they differentiating from it and the other data that is R499 which I have to pay for while I'm not aware of and I don't even know how much is this data to show that I don't know this because it was never part of my contract.

Could you please assist me on this because I don't have money to pay for something that was hidden from me, I was never made aware of this. Thanking you in advance,