Seems easy enough....
Simply end the "lengthy and substantial relationship" and use another bank.... and be very vocal about it. Talk to the local manager, any VP that you can get in touch with, write them a letter and send it to your local branch and headquarters. Detail your history, tell them how much money they've made from you and how they're not going to make another dime. It likely won't change anything, and I'd close business with them even if they offered at this point, but you'll get your displeasure across effectively.
I quit using BoA years ago and never will again.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.