How do you get ash's number in soul silver?

Answer 1

First of all, Ash is not In Any of the cannon (Main) games. He is a character made for the anime/manga. I think what you mean is Red. You can't get his phone number in Heartgold/ Soulsilver, but you can Battle him at the top of Mt. Silver, a place unlocked after you defeat all the gyms in Johto and Kanto. After you defeat him, the only way you can battle him again is to defeat the elite four again.