What a distressing story. The collection agencies are happy to pick on those who do not have the resources to defend themselves. The bank is happy to let your balance go negative, because it permits them to rack up fees. The interests of the customer (you) do not even register as a footnote.

Good on you for closing that account, and clawing your way back to solvency. One day you'll be wealthy, and that same bank will come a-knockin'. Tell them to go pound sand.