I want to change my Apple ID to Gmail but it says email in use?
I want to change my Apple ID from yahoo to gmail but it says email in use? It’s me using both emails.
iPhone 13
Perhaps at some point when you tried to change the email address used for Apple ID
the original or first one had not been disassociated correctly; and so it's still active(?)
Manage and use your Apple ID - Apple Support
//support.apple.com/en-us/HT203993
Links through Related Article above your thread have some ideas; if used to their depth.
[The related link ^ above goes to: Change your Apple ID - Apple Support]
About your Apple ID email addresses - Apple Support
//support.apple.com/en-us/HT201356
These partial changes evidently cause issues; & may cause havoc.
To login to Apple ID (page for iCloud) online could help, to a point.
Check and see how login through any browser to access your iCloud.
Manage your Apple ID - Apple Support (sign-in)
Sign in with your Apple ID - Apple Support (info details about above sign-in)
//support.apple.com/en-us/HT204053
(Not sure how to proceed here; my 'non-volunteer life' needs my attention now.)