Lie from representative regarding annual fee: any recourse?

When the annual fee rose, I called prior to my renewal date to ask to switch to a lower-fee card. The representative offered me a significant discount on the annual fee. To my great surprise, I was subsequently charged the $795 annual fee. I called to resolve this, and I am being told that there is no way for them to honor the offer given over the phone. Has anyone else had this experience? I am very frustrated.