phone is on activation lock

See the article If you forgot your Apple ID email address or phone number - Apple Support

Read the section- Other ways to find your Apple ID

Check your inbox for emails from Apple

If you found the mail address that is an Apple ID see the article Activation Lock for iPhone, iPad, and iPod touch - Apple Support

How to remove Activation Lock - Apple Support

Start a support request

If you need help removing Activation Lock and have proof of purchase documentation, you can start an Activation Lock support request.

Check your web browser autofill entries and other records, or use Apple's iForgot service, or contact their Account Security team, or if you're the unit's original owner, click here and submit an unlock request.

(217081)