How do I change my Activision ID?

Link Up to Earn Rewards in Call of Duty®: Mobile

So I just got warzone, and I need to create an Activision account, as this is the first time it's required. I try to enter in my information, but it says invalid

HackMD - Collaborative Markdown Knowledge Base

Modern Warfare 2 “Activision account could not be linked” error: How to fix, possible reasons, and more

Keeping your Activision Account Secure

Activision Account Hacked: How to Recover It? - MiniTool Partition Wizard

Modern Warfare Activision ID: 5 Things to Know

How To Close An Activision Account When Someone Dies

500,000 Activision accounts have been leaked

Call of Duty: Warzone cross platform explained - how to enable and disable cross play on PS4, Xbox and PC