American here.
I don't know about the 'dishonest' part, but when we overdraft we usually get dinged for an extra $30 or thereabouts on top of the transaction amount -- and that's per-transaction, not just a one-time fee for going over.
Those add up *fast*.
Not sure if that's how it works in other countries.
(Let's not even get into banks selling what they call "overdraft protection" which does not do what it says on the tin but rather, for a flat fee, means they charge you a little less when you overdraft.)