Thanks. I went ahead and called. The music is often static-y when I call. Maybe it's just my phone but it's literally been that way for years.
I had to select options several times
1. To select English
2. To select Disney World in Florida
3. To select that I already have a reservation
4. To select payments
5. To select that I don't know the extension number of a cast member to speak with
It took about 25 minutes (including the time it took to select the options above) to be connected with a cast member. So the total time was about half an hour.
I just wish there was a way to do it online. I could have sworn I used to be able to pay it online, many years ago-even without a package.
Edited to add: I wanted to use redemption rewards from my Chase Disney visa to pay the room balance, so that's why I wanted to pay it off before my arrival date, instead of just letting my card on file be automatically charged.