I changed my phone number and can’t log into my Apple account

I've been trying to help a friend with this very issue. I finally got in a chat tonight at Apple and the gentleman eventually sent me to iforgot.apple.com. By continuing to choose that I couldn't use the old phone number and didn't want to use a friend's device I eventually got to use the email address for the verification and then change the phone number. Then got a verification on the new number. Now we have to wait for Apple to research that it's her iPad (by this time we had it totally locked up due to forgotten passcode) but I have hopes in a day or so she'll be back in business. The gentleman in the chat said it would go faster if we used one of my devices, but I was hesitant to do that. If you have another Apple device or a friend with one, that should be immediate (I think). Anyway, good luck!

Sign in to your Apple ID account page and edit / update your Apple ID details -> https://appleid.apple.com

• (Sidebar) Click Personal Information -> Reachable at -> then edit / update your trusted phone number.