Paying for data I don't receive

I have been paying for data for a Vodacom contract since 01-04-2017 and I have never received it nor the sim card that us supposed to be loaded on. When I ask them to cancel the contract they said I will pay the cost of the contract for the remaining period which is over a year. The rude consultant said or I can buy a sim card and do a sim swap for an additional cost of R80.00. She refused to check on the system if that sim card ever worked or if the data from April is there. When I call their contact centre they refer me to a branch and the branch always chase me away... I don't know what to do because every month they take my money but I don't receive the service and if I don't pay they say they going to blacklist me