I dealt with a very similar situation last year around Christmas. Dude started blowing up my phone early one morning. I sent him a message via eBay stating that all communications regarding an auctioned item need to be handled strictly through eBay messaging. He still called. I spoke with an eBay rep who agreed that ALL communication needs to be handled via messaging. The phone number is only to be used by the buyer when the seller refuses to communicate through messaging.