I don't see it as a typo. Bank is being used as a verbed form of "use banking services", and the text that follows provides an example of how using only a single banking service provider can screw you over.
The semantics of "how you <do thing> can screw you over" is still a bit odd, as "screw over" is typically done by people in the English language ("the mailman screwed me over" reads better than "the mailbox screwed me over" or "how I closed the mailbox screwed me over"), but that's less egregious than the obvious typo I took it for (assuming noun form of "bank"). I digress...