How do you close a checking account?

My wife and son use to have a checking account at a bank here in Brookline ,Ma.Her check was directed deposited,however I lost my job and I had to go and take and earlyer s/s retirement in order to pay the rent to keep a roof over the familey head.At one time when the money was good the creditors were takeing there mouthly payments out of her account. She tryed to close the account,out but the bank would not let her close the account out.Now she has a new bank account at a differant bank and her check goes to that bank now. Now Brookline bank want her to take out a loan in order to pay the bank off of the NSF that have happen from the time she open another account with another bank.And her paycheck goes to that bank.Is this legal for the bank to do this?She tryed to close the account out four mouths before this happen but the bank would not let her close the account because at that all she owe the bank was $300.00 NOW ITS ABOUT $700.00.I am thinking about going to a lawyeron this matter.