Someone is using an appleid i created and changed the phone number. How do I fix?

See if anything here helps.  If necessary, you can use account recovery as explained in the link at bottom of the article.

Verification code - how to get one and sign in with two-factor authentication.   *

If you can get a code and sign in, you need to change/add the number on your Apple ID. Look in the Security section when signed in online. You may have to add the new number before you can remove the old number. After the change, allow up to 24 hours for the change to sync. Before trying to make the change, sign out of Messages/FaceTime on all devices/computers.

Apple ID - Manage

You might want to consider changing your Apple ID password and making sure it is a strong one. If the attempts continue, you might want to consider a name change.

Link to contact Apple Support in the article.

Apple ID has been compromised.      *

Personal Safety User Guide

Security and your Apple ID.   *

Checklist: If you want to see if anyone else has access to your device or accounts  *

 Apple ID Password Change.  -

ASC YouTube for How to reset your Apple ID password

You can change your Apple ID email address on your current Apple ID so you retain access to your data and prior purchases. Note the restrictions in the article.

Apple ID Name Change.  * 

Make sure you turn off Find My Phone before signing out of the old ID. Once signed out and Find My Phone is off, then sign in with the new ID, then turn Find My Phone back on.

 What to do after you change your Apple ID or password - Apple Support  *  I suggest doing this before you change your Apple ID or password.