www.bungie.net | halo.bungie.net | bungiestore.com
And the Shadow fell upon the Land, and the World was riven stone from stone. The oceans fled, and the mountains were swallowed up, and the nations were scattered to the eight corners of the World. The moon was blood, and the sun was as ashes. The seas boiled, and the living envied the dead. All was shattered, and all but memory lost, and one memory above all others, of him who brought the Shadow and the Breaking of the World. And him they named Dragon.
No.
Sorry, you're out of luck. Your only option is to make a new account.
Ad Astra Per AsperaExperienced In Life's Little Drama
The only way is to ask Achronos if you can change it........but, you would have better odds of being made b.net overlord than having your name changed by him.