Orange did something worse than that to me..I paid my bill of, closed the account & they did not update my credit file so I was not able to get a mortgage

I had a Gold account with Natwest, the account went overdrawn because of the Account fee & I was never notified by Natwest & never heard from them for over 7 months & could no longer see my personal account so gathered that they had closed it due to inactivity. I also had a business & savings account with Natwest. On Friday last week, my personal account appeared on my mobile banking app as out of nowhere to say that my personal account was £2k overdrawn. I went to pay money into my business account & was told that my business debit card had been stopped & was told to ring 0845 301 5139, which turned out to be Triton Credit Services. The guy I spoke to said my card was stopped as my personal account was £2k overdrawn due to accumulated bank charges & that they (Triton) wrote to in January this year. Well first of all I am very confident that its illegal for banks to charge on charges & secondly I received no letter from Triton. I was contemplating asking to see a manager to see if I could come to some arrangement with Natwest but from what I have read on here there does not seem to be much point. Any suggestions on where I go from here would be gratefully appreciated