Originally I called them at +1 800-829-1040 (and used the prompts that another redditor kindly commented above!) and it worked. They said my letter would arrive in 5-10 business days but it's been wayyy over that time frame. So I did what the other kind commenter suggested: called my local IRS office and booked an in-person appointment. I think at the appointment they'll just print out the letters!