Disappointed about Fnb forcing an unsigned agreement on me.

I upgraded my gold credit card to private clients credit card on fnb App thinking I will get some cash back. i realized there was no money that I will get and used chat to ask them to downgrade it as it gives you 7days to cancel if you not happy with it. They could not help me. I received an Email Fnb asking me to sign the agreement for private cc i responded that I won't sign any agreement because I don't want this credit card they must downgrade to gold as it was before. They responded that I needed to pay the balance they transferred from gold cc to this private cc. I tried to explain that I will be paying my credit card monthly as before but they refused. Right now I am forced to pay the high interest on a cc which I never used I emailed them that I will seek legal advice about this. They went ahead and closed my gold cc now.. Something that I never asked them to do.