Call of Duty: Warzone is a new game mode of Call of Duty: Modern Warfare, and can only be installed separately if you do not own Modern Warfare.
Troubleshooting error BLZBNTBNA000000CA
Information for troubleshooting Modern Warfare in-game technical issues
Information on Blizzard Phone Notifications
Information about how to unlink your Activision account from your Blizzard account
What to do if you are missing items purchased with CP.
Read Activision's FAQ for more information on pre-purchasing Call of Duty: Modern Warfare.
Information about purchasing Call of Duty in another region.
How to resolve this error when adding a phone number to your Blizzard account
Information on the Blizzard Authenticator