Apple ID log in problem. Trusted device, phone number not available.

I'm posting this question on behalf of my son.

A few months ago he lost his iPad (which was his "trusted Apple device"). He has also recently changed his phone number.

He is now trying to sign into Apple Music, but seeing that two factor authentication is switched on, he can't sign in because an OTP type number is sent to his old phone number.

Although he has the Apple ID and password, he can't sign in. We can't get to a page to switch off two factor authentication or get into the account.

Can someone pls send a link where we can recover the account. He has no Apple devices. I have an iPhone and a Mac.

Tks,