I had problems with my bank last year. Same crap, no response, rude people, I even contacted the Federal reserve bank (They're a joke). So I decided to handle the matter myself. I took them with NO attorney to small claims court and WON! If you know the situation and you have your documentation (MUST have documentation) then GO FOR IT!
Bank ended up paying me what they owed plus the attorney THEY hired, plus court costs and THEIR attorney hired a court reporter they had to pay for. When my name was announced in court and then the bank's, people turned around and looked me like I was crazy and I am, like a fox.
So I suggest you go to small claims and in the meantime let them know harrassment is against the law. If possible change your phone number or screen your calls. Good Luck!