Bad network and cancelling contract

Took out a contract data sim in may. Wasnt told the sim was activate when i received it. Now 10 june 2019. Now i havent used the sim but is being charged from date sim arrived. Now i want to cancel it. Im unable to. I have to pay 24 months in advance for a sim i havent used. They let me wait on the line for 50 min. To sort out my contract. Telkom is not helpfull in anyway. Regret agreeing to a sim card which would have made uaing data simple but now im struggling to cancel the contract.