If you have any remaining tokens you can change it yourself via settings. If you don't have any then Bungie don't offer them on request, you could try filling in a [url=https://help.bungie.net/hc/en-us/articles/360049024632-Contact-Form-Data-Privacy-Requests]privacy request[/url] but that (if accepted) only gets you changed to Guardian. You do not get to pick your own name via this method.