Trusted Phone Number & Two-Step Authentication

You only have one trusted phone number?

Note: You should have more than 1 trusted phone number.

FYI: You can use landline number or from a trusted relative/friend.

If I can't sign in, how do I regain access to my account?

If you can’t sign in, access a trusted device, reset your password, or receive verification codes, you can request account recovery to regain access to your account. Account recovery is an automatic process designed to get you back in to your account as quickly as possible while denying access to anyone who might be pretending to be you. It might take a few days—or longer—depending on what specific account information you can provide to verify your identity.

See if anything here helps.

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