OT: cellphones in the US

[tnas at euronet.nl]

Hi all,

Please reply privately, as this has nothing to do with Audis in a direct way,,,

Here in Holland, you can buy a cellphone with pre-paid call tariff. You buy a phone for peanuts and 
you get a certain amount's worth of calls with it. When you've used that up, you can upgrade the 
account by buying a new card and entering a code into the phone. The provider relies on you 
upgrading your account regularly for the profit in this deal.

Does this system also exist in the US, and what do phones generally cost? For a CA trip, which 
phone networks are best? Or would it be a better idea to buy a tri-band phone here and rely on my 
network's roaming service?

TIA for your replies!

Regards, Tom