Owner is sueing me for rent I paid in cash, because he thinks I called the fire marshall when I left.?

I rent at a salon and the owner didn't give me a receipt when I paid rent in May. June I gave my 30 day notice with my rent. On my last day the owner tells me I owe him since I didn't ask for a receipt I have no proof. We hashed it out. I heard the Fire Marshall and city went in and fined him and he blames me. Now since Aug 12th he is sueing me. I don't have proof, just a pattern (if I don't pay, he takes it out of my income) I did pay, but am being retaliated against. What can I do but tell the truth, I don't want a judgement.