ESA and Service Animal Question???

[Kathi Miller]

Hello, I recently (May) signed a 6 month lease with a couple who straight up told me they have no pets, as I have a no pet policy. They are to move in Sept 4th. They called me yesterday, Aug 1, to tell me they have an ESA dog. A large one, 50 lbs. They went on to tell me that they didn't try to hide this from me, but didn't want to disclose because of my policy... also that I couldn't charge any additional damage deposit or deny them renting the home. I have never dealt with a situation like this. What are my rights as a landlord? All I asked for was that they give me an additional $300 deposit and I let them know that I denied a lease to another couple for a longer term lease who were upfront with me that they had a small 8 lb dog and wouldn't have had a vacancy for the month of August. Any suggestions or advice? I feel completely duped.

Thank you!

Kathi