I thanked the rep and did exactly as they said, including confirming my correct address with said rep when it was done.
My connection changed to Bigpipe hours later. Unexpected, but brilliant.
I supplied Bigpipe with my correct billing address via chat at signup, and they managed to connect me correctly.
I asked via chat 2 weeks ago for my billing address to be corrected, I even supplied a transcript of the original chat. I was assured it would be fixed.
It's now a month since I signed up, and it still hasn't been fixed. so now I have a bill with the incorrect address on it.
Bigpipe were excellent at signup time, and fixed my connection smartly when I couldn't connect originally. But this seemingly simple problem remains unsolved.