Glenn, I can call Alltel and shut off, or turn on, my $59.99 monthly service at will. I don't have to pay the monthly fee every month, if I don't want to - unlike a contract, which will charge you every month for two years, whether you are using that service or not. If I am at a WiFi spot for more than a week, I can keep it off, and not pay for it, then call them and have them turn it back on if I am going to be in a non-WiFi area for a while - like I am now.
Hope that was as clear as mud???