Poor service and being mislead

I am very disappointed with FNB. I was sold a FNB sim card under fails pretences. I have been waiting for someone to call me for a week now. I was told to send a cancellation email which i have done got a automated response saying someone will call me back shortly well i am still waiting. When I called to follow up the lady I spoke to said there emails are so back logged and she can tell me now that someone wont get back to me shortly also to tellme that i will be charged a penalty fee for cancelling( dont see why i must pay a cancellation fee as I did not want the FNB sim in the first place). Whilst I am waiting I am still liable to pay the sim which I do not want.