For violation of employment contract they will not file any police complaint. If they do it, counter it by saying that the manager had asked you to resign and there were pressure from his side to resign and you did it with good faith without knowing that the bank would use to make profit out of it. There is no need to prove that you were harassed because this practice is known to every one in the industry. Take that stand.
Legal action, anyway, will depend upon the Bank's policies evidenced by appointment letter or standing orders. You can approach a good labour lawyer and discuss the issue so that you can legally fight.