Were you logging on to the "genuine" bank site or a fake copy.
If it was a fake copy then whoever runs the "fake copy" site now has your ID, passcode and reg number so can now logon to the official site and steal all your money !
This happened when I bought a new computer. Not having any details I just googled my bank. Apparently when you do this the fake/rogue websites appear at the top of the list. It took me 10 hours and three phone calls to resolve the issue.