How can I help my best friend through a recent breakup?

My best friend moved up here from Alabama, and before he moved, he was in love with his girlfriend. They stayed in contact, and planned to get back together one day. I realize that doesn’t always work out, but still.
She got mad at him, for one reason or another, and got a new boyfriend.
I’m really worried about him. He won’t even talk to me anymore, and he’s really sad… I’m his best friend. I thought if he’d talk to anyone, it would be me… I want to help him, but I don’t know how to do that. He won’t answer my phone calls, or my texts.
I don’t know what to do… :’(