Squeaky wheel gets the grease...so keep on em.
Ask for supervisors, handlers, processors, any higher up that can get the situation fixed. Don't go away or hang up or agree with any brush offs. Hound them, and have your proof of the correct tax rate and estimated escrows handy to show them.
There should be a process to dispute the calculation, which may include arbitration and/or mediation by a third party. I'd google and ask around until I figured out what I needed to do, because I would bet cold cash BoA won't tell you up front.
Good luck!
Note: I learned a lot about how to get CS to respond when I had a serious issue with service at Verizon. I found out there is a 'secret' (ie: not public) department there whose sole function is to 'handle' the squeaky wheels who won't go away quietly
