Charging for a \benefit\" that I dont know about"

This month I got a sms from sterns saying that my account is in a rear after I payed the full outstanding amount last month. When I phoned the call centre I was told that there is a benefit on the card but they could not tell me what benefit it was and I was told to phone the call centre. I tried to phone the call centre but apparently its impossible to speak to someone unless you \Enter your card number followed by the # key\". When the lady from sterns sold the account to me she specifically told me that the account would cost me nothing per month. Otherwise I would have never opened the account.I have probably been paying for this \"benefit\" for a couple of months now without even knowing what it is for."