That's odd. My sequence is different, but the end result worked just fine.

I was with Cingular with my original number I then was transferred into AT&T I puchased my iphone, still the same original number. I then changed my number.

When I entered in my number, I used my new number. That worked ok. However, the difference here is I changed my number within the AT&T network.

In your case, you moved a vonage number, into your iPhone.