The funniest part of the entire call was the guy's insistence that he could downgrade the plans for the numbers I had on my account (3 of them at the time of cancellation), after they were already ported away from my account and Vonage therefore having no legal control over them. Almost as funny were his repeated attempts at offering me other things to try to get me to stay (or come back, considering the aforementioned number porting). I knew that there was no way in hell, though, that he could come up with anything usable that would match what I'm paying now.
After my repeating the news about the number porting at least twice, and just flat out saying "No" at least 3 times, he finally agreed to disconnect my service and wrap things up. You'd think that these guy's paychecks were being docked for every customer they lost.
Hopefully I don't fall into the same pain that others have mentioned of being billed by Vonage after service was disconnected, or having their numbers kept around in Vonage's database so no one in their network could call the numbers even though they were being hosted somewhere else. That one in particular can be tested rather easily, though. If any of you Vonage customers that see this want to help, let me know and I can send you my digits and you can see if you get through.
In case I fall into the "billed for nothing" crap, I've already got hard copies of the disconnection emails and billing stuff from their website, ready to fax. In fact, I may go ahead and use the private fax-to-email that I can do these days to get an emailable PDF of those ready to send... again, just in case.