Unable to access old phone number linked to Apple ID for account recovery

If you can still sign into your account on another device you can investigate adding more ways to get a code such as multiple telephone numbers where you can receive a text or a phone call. The below is based on the section "About trusted phone numbers and trusted devices" in the article Two-factor authentication for Apple Account - Apple Support

To see, add, or change your trusted phone numbers use one of these methods:

● On your iPhone, iPad, or iPod touch: Go to Settings > your name > Sign-In & Security. Tap Two-Factor Authentication, tap Edit (above the list of trusted phone numbers), then enter your device passcode when prompted. Add or remove the number, then tap Done.

● On a Mac computer choose Apple menu  > System Settings (or System Preferences), then click your name (or Apple ID). Click Sign-In & Security, then add or remove a trusted phone number.

● Using a web browser:

1) Go to https://account.apple.com and sign in.

2) Follow Account Security options until you find one letting you change trusted numbers,

3) Click "+" to add a new number (you may be required to verify this number).

4) If you wish to remove an old number, click "-" next to the number.

If you find you can’t sign in, reset your password, or receive verification codes, you can request account recovery (get Apple’s own instructions in this article: How to use account recovery when you can’t reset your Apple Account password - Apple Support ) to regain access to your account. Account recovery might take a few days or longer, depending on the specific account information you can provide to verify your identity. One tip to using account recovery it to look for options in small blue letters beneath the normal log-in items if you cannot complete the requested information.