請教老貓

I, tenant, paid rent on time. Landlord turned me over to its collection company with a small balance and indicated it was over due, I paid it, and paid on time. the check was cleared long time ago. I have a copy of the orginal check. I am writing to the Landlord and Credit bureaus to fix my credit. I have no idea how long takes to remedy my credit. In addition, it is really time consuming, and create financial loss to me. Is there any way I can file a complaint of the Landlord?

Thanks a lot