I ask people to call me. I talk faster than I type. 90% don't seem to know how to use a telephone except as a typewriter. Keeps the workload down. If they don't have the ambition to talk, I don't have the ambition to type.
Any sale over $1000 between states that goes unpaid is a felony. Call your local authorities and turn him in. They will coordinate with his local authorities. I've had to do this with a forum member. It worked.