Poor service

I have a data sim which when I app**** for, I was told that it’s a month-to-month sim which I can cancel anytime but now I’m being given excuses that I must pay R4999 if I want to cancel that I don’t understand because this is just a sim card with no phone and I did not sign any agreement. The sim card does not connect I have so much data that I cannot even use so meaning I am being ****** by Cell C because I am not getting the service that I am paying for, hence my reason for wanting to cancel. I have been given a run around for 2 weeks with the connection issue that I’m exhausted.