The easiest way to pay would be a paypal account. If ou have a bank account you can set up paypal to a credit, debit or to withdraw from your bank account. Check out www.paypal.com, once set up you can go to ebay and search for usb modems.
I just got mine yesterday and I am setting it up today!
Then you can get any old dial up provider, AOL, Netzero, Juno, look around since the place you connect should be with a company that has a local number so you do not incur any long distance charges. And on that note make sure that your local service is unlimited too.
Good luck!