Signed up for a forex broker account years ago, deposited some funds, just left the account untouched. Decided to trade recently but realised my funds are gone due to "inactivity fees". Please help?

Since the salesperson said that my money will be safe in there for as long as I learn to trade (I was young and noob, still learning to trade at that time), I just left the account sitting there untouched. The "inactivity fees" thing was introduced a few years after I signed up, and they only informed about it in an email, which I totally missed. How can I challenge that action and recover my money?