What do i do with a harassing landlord?

I would write a letter to the LL, be very nice, and explain that there is a misunderstanding. Say you didn't do it, and assure them they have no reason to worry about you causing any problems in the future. Put the date on the letter, sign it, and make a copy to keep in a folder. Save the voicemail they left you, too. By the way, they cannot evict you without filing a court case, serving you with the papers, and having a hearing. If you ever get served eviction papers, call a lawyer - and you should start with Iowa Legal Aid - if they take your case they work for free.