Apple ID verification codes via text message

If they are truly text messages and not alert dialogs they may be scams. The other possibility is that someone is trying to hack your Apple ID, and already knows your Apple ID’s password. So the safe thing to do is to change your Apple ID password → Change your Apple ID password - Apple Support

If they are truly text messages (Green Bubble) forward them to 7726 (SPAM) so your carrier can deal with them. Do they have a link in them?

Very strange. Could anyone else have used your phone number as a backup trusted number for 2 factor authentication? For example, my wife has mine as a trusted number, and I have hers.

ah ha! The previous owner of that number probably used it as a trusted number and never removed it.

What happens if you tap on the code?

those are not what authorization codes from Apple look like.

As you’ve changed your password it should be safe to give them one code, and tell them to change the trusted phone number.