Changing billing address on the Apple ID site

This still does not seem to be answered, after looking at 4 different threads. Within Wallet on my phone the address is correct. When I go to try and manage my Apple ID on a Mac (NOT on my phone) on the Apple website, the SHIPPING address is correct, but I have no option to update the BILLING address. The pull-down to select the country and start the process does not allow any entry, like all the other text boxes. It actually has my almost two-year-old address in it, and yet surprisingly it's never caused an issue. But the correct address needs to be there.

How can it be corrected???

Thanks,

Philip