What is your most successful response to turning down a man?

I am a lesbian and i have made the mistake of telling guys this. This never makes them stop the flirting- they get intrigued or just straight don’t believe me.

I want to say something that would stop the conversation like immediately and preferably I don’t have to offend or disgust them. What are y’all saying to turn down men? Should I get a ring and say I have a husband 😭