You can buy a netbook outright. That is how it started. The whole phone service thing was just a market that the phone providers saw and they pounced on it. All it is is a netbook with a particular provider's phone card built in. I would highly recommend you buy the netbook of your choice and if you want to connect....the aircard of your choice(or tether your smartphone via the software I provided above).
I will backtrack a bit. A netbook is just a small stripped down cheap computer. It has nothing to do with cellphone companies. It's main purpose is for basic netsurfing and extreme portability....has nothing to do with connectivity. Again, the phone companies saw an opportunity and they took it.
So if you want a small very portable cheap computer, get you a netbook(I would highly recommend ASUS). If you want connectivity thru that netbook, get you a phone card thru your provider of choice. If you want a more fully functioning computer, get a standard laptop. And get connectivity thru an aircard if you want.....or tether thru your smartphone.
It just seemed that you thought netbooks were synonymous with connectivity....and they are not and have nothing to do with it other than provide a smaller more portable platform for air cards and "marketing bundles".