Do I have a defamation of character case.

The car finance company I was with fired their managers and brought in new ones and I was called and told I was behind on my car payments,I told them no that their finance company owed me a 1000.00 dol for a repo I had did for their previous manager.They told me they would not honor it and that I needed to make a payment or be up for repo.I refused to make a payment and hung up after three months they finally called me and requested payment at that time I tried to settle with them and they still denied they owed me so I just hung up the phone,with in two weeks I got a call telling me I was under criminal investigation and threatened to tell everyone I know.Then a realtor called them to get a refrance from prev. manager and they told her i was a criminal and under investigation etc.