If this were me, this is what I would do:
You need to call / go into your bank immediately and inform them of the unauthorised charge. There will likely be forms to fill out. I know with my US bank, they immediately returned the charges when this happened to me, pending the outcome of the investigation (i.e. had the charged proven to be real, they'd take the money back just as swift).
I don't have the same faith in banks here, however you NEED to get in touch with your back super quick!
Then you need to contact your landlord. It would be best if you had something in writing from your bank to back up your claims, should your landlord request it. Alternatively you'll just have to pay the late fees later on, I guess.
Hopefully you have also changed all of your logins, passwords etc...