Repairs not attended to

For the last few months, I have been dealing with National Letting to repair a ceiling in the apartment I am renting. All attempts to get this fix done has gotten me nothing but excuses and deflection, with them blaming the owner of the property, for the repair not happening yet. The owner, whom I have never dealt with or met. They do not seem to have an idea as to what their responsibilities are, in terms of the contract, or more appropriately just choose to ignore it. I have been dealing with Lauretta Slabber and their support desk, to no avail.