Why do I need a Battle.net account?
A Battle.net account is required to play Overwatch 2 on all platforms anyway, so you'll need to create an account regardless if you don't already have one. PC players will already be playing on a Battle.net account, but console users may need to set one up.
Internet Connection, Blizzard® Battle.net® Desktop app and registration required to play. A mobile phone number must be linked to your Blizzard® Battle.net® account to play Warzone for free.
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If you wish to delete your account, you may create a request to remove personal information from your account. Proceeding with this erasure request will permanently remove all personal information from your Battle.net Account. Information that will be removed includes: Name.
This naturally isn't necessary if you only play on PC, but if you play on console then you'll need to go through this process. It's important to note that you can only link one console account per platform to your Battle.net account for transferring progress.
Step 1: Load up Overwatch 2 on the console you wish to merge accounts on and sign in. Step 2: Select Options. Step 3: Scroll and select Link account. Step 4: Use your mobile device to scan the QR code.
A Battle.net account can be linked to an Activision account to track your Call of Duty profile. If you do not have an Activision account, you can create your free account here. In the ACCOUNT LINKING section, choose an account to link.
Blizzard accounts can be linked to an Activision/Call of Duty profile. If you do not have an Activision/Call of Duty profile, you can create a free one. Select CONTINUE. You will be taken back to the Blizzard website to complete the account linking process.
With the introduction of crossplay in Call of Duty: Modern Warfare, players who wish to play online are now required to log in to an Activision account. Accounts make cross-platform play possible, allowing you to play online game modes with your friends on all platforms.
Battle.net is an Internet-based online game, social networking service, digital distribution, and digital rights management platform developed by Blizzard Entertainment.
How do I remove my credit card from Blizzard?
You can delete any payment information saved on your Battle.net account by visiting your Payment and Subscription page.
Blizzard states that requests to delete your blizzard account may take up to 30 days to complete. Although it's a bit annoying to have to wait up to 30 days, once the process is finished the deletion is permanent. My Blizzard account was deleted after 9 days and I received an email from them confirming this.

The phone verification system, which Activision Blizzard calls SMS Protect, is meant to cut down on toxic behavior from players, preventing them from creating endless new accounts to evade bans or to cheat.
You may use the Platform for your personal and non-commercial entertainment purposes only, unless specifically allowed under the terms of this Agreement. You may not transfer your rights and obligations to use the Platform.
Modern World of Warcraft, WoW Classic, and Burning Crusade Classic are all installed through the Battle.net desktop app. Each game version must be installed separately.