Finally have the new phone connected to my old number and all’s well with the world. (Mercury went direct at 6:11 a.m. today. Thank you for not flogging me anymore.)
UPDATE: I spoke too soon. I am now convinced that businesses make dealing with their customer service departments an ordeal on general principles. The phone number is not actually working yet. Just like before, I can make calls out, but I’m not getting calls in.
UPDATE: I had another chat with my new best friends in the offshore tech support center. It turns out that no one ever bothered to enter the data plan for the phone, so the web access wasn’t working. I think I may have found a company that’s actually worse than Comcast.