Regain account when forgot old phone number

Welcome and thank you for reaching out. 🤗

According to Apple:

On your iPhone, iPad or Mac:

1. Go to Settings or System Settings, then choose [your name].
2. Tap or click Sign-In & Security.
3. Tap or click your primary phone number to make changes.
4. To remove this phone number from your account, select Remove from Account. If you want to keep the current phone number associated with your Apple Account but change to a different primary phone number, turn off Primary Phone Number.
5. You’re prompted to choose another primary phone number. You can choose one of your other phone numbers already associated with your account as the new primary or add a new primary phone number.
6. Follow the onscreen steps to enter and verify your new primary phone number.

If your new mobile phone number is already connected to your Apple Account as a Messages phone number, shared phone number or trusted phone number, then you don’t need to verify it.

On the web:

The easiest way to change the primary phone number associated with your Apple Account is with your iPhone or other trusted device. A trusted device is an Apple device that’s already signed in to your Apple Account using two-factor authentication, so that we know it’s yours.

1. Go to account.apple.com and sign in to your Apple Account.
2. Go to Sign-In and Security, click Apple Account.
3. Enter the mobile phone number that you want to sign in to your Apple Account, then select Change Apple Account. 
4. A verification code is sent to you at that number. Enter the verification code from the text into the fields provided.

If you need more help, contact Apple Support directly.

Thanks again for reaching out. 👍🏼

Good Luck! 👋🏼😉

Smiliñ 😎 Brian | Community Volunteer