I moved it for the first time myself when I transferred to T-Mobile when ATT started charging too much. Then for awhile I had no cell phone at all, and that number moved to Vonage, where its been since 2002.
Well, I'm cutting back on services, so Vonage was just taken out. To my surprise I was able to move my number yet again to Net10, where it will soon live on one of those pay as you go cell phones. I'm really surprised that worked, especially them mailing me a new sim card to enable it for free. On one of these. So I will still have that number. Conveniently I never got around to memorising the old one.