The guide to linking and unlinking accounts is [url=http://www.bungie.net/7_How-do-I-linkunlink-my-account-on-Bungienet/en/Help/Article/12130]here[/url], however the bigger concern is that the Microsoft Account that you linked (which you say is your only one) is for whatever reason not associating with the Gamertag you use to play Destiny with. I'm not a Bungie Employee, but I doubt that unlinking and relinking the account will solve your problem. I'd verify that the Microsoft Account is indeed attached to the Gamertag you play Destiny with, if that's the case we can explore other options.