Microsoft, Sony, and Steam accounts can be linked or unlinked by visiting the profile section of the Call of Duty site.
  1. Click the gear icon and select Profile.

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  2. Scroll down to the Consoles section to link or unlink a console. To link, select a console you wish to link. To unlink, select a linked console.

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When linking an account, you will be temporarily taken to the console manufacturer's website to confirm your credentials. Once confirmed, your console will be linked to your Call of Duty account.