So many people have posted their Phone Number is connected to another account which they cannot access and are unable to use their Number on their Current account. This is how you fix this issue.
Click on “Can’t Log in option”
Click on “Forgot Email Address”
Put in your Mobile Number that is registered.
It will send you a verification code and then unlock the email the Phone number is currently attached to.
From there you can log in from your old email address and remove the number.