Can't sign in - no access to 2F auth mobile number
I have a new phone. It's a pay as you go and at some point since setting up the 2 factor authentification on my old phone I have changed the number. My new device is not signed in. It will only let me sign in by sending the code to the old phone number. I tried logging in online and it will only allow me to sign in by sending a code to the old phone number. I have tried "forgot your password" (i know my password) and it wants to send a code to my old number. I have tried "https://iforgot.apple.com/" and it wants to send a code to my old number.
I can't sign in to change that number. I can't sign in to add a 2nd number to the account. I can't reset my password without sending a code to the old number.
I don't have access to the old number.
What can I do?
iPhone 8 Plus