thank you for sharing your question with the Wefugees Community.
It depends on which German institution has given you the flat and pays for the rent.
Mostly if you are during the asylam process, the flats are provided by Social Affairs Office (Sozialamt). In this case, you should complain about it orally or better in written form to the Social Affairs Office.
Sometimes even if you have already received a positive answer from the Federal Migration Office and you are in Jobcenter, the Social Affairs Office will give you the flat but the Jobcenter pays for the rent. In such a case you should complain both to the Social Affairs Office and to the Jobcenter.
If you are in Jobcenter and you have found the flat by yourself and the Jobcenter pays for the rent. Depending on the Problem you should complain either to the landlord or to the Jobcenter or to both of them.
I hope my answer was useful for you and I'll be very pleased if you contact me again with further questions. I'm a member of the MBEON-staff and I‘ll be glad to guide you over a longer period of time. Mbeon is an online consultancy for migrants via the mbeon-app, which you can install on your smartphone for free. Download it via App Store or Google Play Store. You'll find me In the mbeon-app under my name „München, Herr Noori“ and get confidential one-to-one advice in a safe virtual room where nobody can wiretap messages. Further information: www.mbeon.de
With kind regards,