From a friend of mine:

Good news, everyone. Like some of you I've read about, I have a "minutes used" data plan, which is supposed to charge for data just like voice - by the minute, not by K. My plan shows on the website as "NATIONAL ACCESS 600 ANYTIME $75.00 1Y 1002". When I got my Treo 600 last month, Verizon began charging me $.015 per K. I got billed $65 for data my first month, after hardly using it at all! (One woman I spoke to told me that my per-minute data plan was for when I hook my computer to my treo for 'net, but did not apply to using the Treo itself to browse.)

I just got off the phone with them after receiving the heavy bill, and I am quite pleased. The scoop is, apparently they are so unused to my particular data plan, they made a mistake and were charging me for both minutes and K. The nice fellow credited me back the $65 (plus taxes) and removed the per K data feature. He claims that from now on I will be using just minutes, regardless of data amount.

Another thing to look out for: I was still being charged for "Mobile Web", which is (as far as I know) totally useless on the Treo. He removed this feature and credited me back for it, too.

NB: The data plan I have does NOT include a night minutes feature. Meaning, part of the reason my bill just now was so high was because I was making a lot of long late-night calls, without realizing that they weren't included in my 3,000 weekend minutes. But because I had never exceeded my minutes before since I've had the plan (July of last year) he ALSO credited me back for over half of the excess minutes charged - even though it was pretty much my own damn fault.