Problems with your room or your landlord? Or simply looking for a room for next year? Then take a look at the site of the Housing service of the KU Leuven!
For specific problems concerning rental guarantees you can also contact LOKO. You usually only end up at LOKO ater referral from the Housing service.
For more info: https://www.kuleuven.be/english/studentservices/housing-leuven.