Bad service and no help

Around March i was called for a Data contract by Cell C for 10G for 129 , i only get sim card which i was happy with, then month of April i was then debted around 800 which i rejected on my side as i didnt understand why so much money. same day of me rejecting the debt order i called them to better understand what is going on, the agent then explained to me that the contract is open plan. i then logged a case for them and me to listen to the call. this didnt happen, for the moth of April i didnt use the data as i was awaiting for feedback.yesterday the 1500 went off my account which for my account which doesnt make sence as i didnt even use the data for the month pf April, i would like my money back as i still have not listened to the call were i agreeed to open plan and it was never mentioned to me at all. i have been calling all day since morning today anyone is willing to give me feedback or any help