I own a hydraulic supply company. A few months back one of our long-standing clients (11 years) stopped paying his invoices. We repaired and reconditioned their power units, they've paid all their invoices expect 3 that are past due 76 days. He said he'll get me the money but now stopped returning my calls. He's half way across the country so I can't show up to his place of business. How can I get my money?