I have a small business in Ca. A customer in Nevada ordered $3500 worth of merchandise.
He was on N30 and I would run his card every 30 days. This order was the biggest.
A day after he received his merchandise, he calls and complaines. I tried gving him the benefit. I even offered to take the items back. Its been a week or so and he has not called back. His credit card was denied. I have been doing business with this company for a year. What can I do.

You asked this same question in another post. Fr. Chuck answered you the best - take this guy to court and sue him for your losses.

This is the first time I'm suing someone. What kind of court do I need to go to and where do I file the papers. Here in Ca or Nevada where he is?

In Nevada in is local jurisdiction