what does it mean to default my Bank account?

[french266]

I am in dispute at the momment with my bank over some bank charges, basicly the amount that the bank have charged me in total is more than the amount of my overdraft my overdraft is �200 the bank have charged me aprox �400 and my account is now �310 overdrawn so therefore i put it to the bank to close my account and call it quits. They have obvisouly declined this offer. I have therfore told the bank I wanted nothing more to do with them, I sent them all my bank cards, cheque books, paying books etc and told them that if they send anything to me (apart from to tell me that my account is closed) that I would return to sender.

They have now sent me a letter saying that if I don't repay the full amount that they will have to take further action & Default my account.
Please can anyone tell me what they mean by Defaulting my account?

Thank you.