I use Chase, and they tried to get me with this once. I had to call and yell at them and basically asked them how it's possible that they know I don't have funds and still let the transaction go through.

I told them that their systems were faulty, and they told me this was a 'feature' of the account type.

I told them I never asked for such a feature, and expect it to work like every other bank account where it denies transactions based on funds.

They reversed one of the overdraft fees and removed the 'feature' from my account at no cost to me. Now if I don't have funds in my account and try to make a transaction, it gets denied. The way it should be, I haven't paid overdraft fees since then.