Apple ID wouldn’t work because phone number has been altered (is not mine)

recently, I tried to download an app from the appstore only for a nontification that asked for two factor authentication after I entered my passcode. The number ended with two digits of a number that is not mine, therefore I cannot access the code. I created another Apple ID in order to ask this question, for even when logging in I cannot because of this. I cannot download apps, make purchases or login to my Apple ID. However, i do know my gmail used and my password. What steps should I take now? Please help. I am even unable to begin account recovery.