Credit Card Settlement Help

uptheblades

I had an outstanding amount on my credit card to which a debt agency agreed a fee with me over the phone - both the idea of a settlement and the amount suggested by them.

I agreed to this and paid it off knowing that this would clear my debt.

A month on I have a phone call saying that I was made the wrong offer and I will have to pay an extra x amount. Obviously I was left fuming as I feel I have been conned into making a payment. Where do I stand with this? At the end of the day they made me an offer with conditons to which I agreed and that was that. Can they legally now try and get more money out of me?

I found this on the bbc about verbal contracts (everything with this agency is recorded) but would like info from anybody with any idea where I stand.

http://www.bbc.co.uk/consumer/your_rights/court.shtml

Thanks.