Because you authenticated to the wrong account and then chose to continue and confirm that that's the account you wanted to use, you've already accepted that there'll be a 90-day lockout should you disable Cross-Save. Sadly, you should have made sure the accounts were the ones you wanted to use on the final page that gives you a chance to make sure the accounts are the ones you want to use. Unfortunately, for your situation at this time, your only option is to disable Cross-Save, impose the 90-day security lockout, and then head over to your Bungie.net Settings under Accounts & Linking so you can unlink the wrong account and then link the correct one. You'll not be able to avoid the 90-day lockout. After having waited out the lockout, you can reenable Cross-Save. Please make sure when reenabling that you actually read and confirm the accounts that will be set up for Cross-Save before you click the button that tells the system those are the accounts you want to use and to turn on Cross-Save. If you have to disable Cross-Save again, it will impose another 90-day lockout.