I know for a fact that the bank (The uber-evil Bank of America) that holds my mortgage is defrauding me. I have a fifteen day grace, although any payment sent after the beginning of the grace is charged the after-grace fee, without fail, unless I use the "Delivery Confirmation" service offered by the post office (or other carriers).
This has been verified multiple times, and even the post office employees have told me this is a common complaint of mortgage payers.
The problem is, I can't sue Bank of America because I have no proof. If the bank sees the payment come in with confirmed delivery, then they obviously know that I've got my eye on them, and don't try to defraud me.
So, I need a solution - namely I need to mail them payments which only I am aware are being tracked, and then sue them when they attempt to fraudulently charge me. Obviously, I'd need to do this several times to establish a pattern of fraud in court, so the solution can't cost too much (although maybe I get lucky and they offer a big settlement if I keep my mouth shut).