Update from May 2021:

The activation number (888) 652-2342 still works!

I was expecting it to not work as I recently had run into nothing but dead-ends when trying to activate Windows XP, so I was happily surprised it did. When I called, I responded with "It's something else" and "It's something else" before it started moving on with the Installation ID. Like others said, don't do the smartphone option and it'll do it over the phone with ample opportunity to repeat the numbers.

I wanted to load up Office 2003 in a VM to re-experience Office before the Ribbon (although I also love the Ribbon), so I'm happy to be able to do so!