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. *
Have you changed the number on your Apple ID? 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
If you decide use the new ID, when changing to the new ID, there may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos. Then make sure full resolution photos are on the devicer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. See Winston Churchill's response in the below discussion. If possible, also set up Family Sharing between the IDs to keep access to your apps/purchases.
How to switch Apple IDs on your iPhone or iPad.
What to do after you change your Apple ID or password - Apple Support.
How to transfer all files from one iCloud account to another.
Family Sharing.
Family Sharing - Set up.