iberia9: they can sue me if they want!!
I can understand you feeling upset at an account fee that you were unaware of would be charged, however what would they sue you for? Your account has been debited, rightly or wrongly, and will stay that way until paid off or refunded.
A good test of whether the fee was clear or not is to revisit the account particulars with the benefit of hindsight and check how obvious the fee was.
Is this their Gold account and are they saying you haven't met the funding requirement?