Your bill is either postpaid or prepaid, depending on the SIM card or rental plan you choose.
Postpaid works the same as your home phone. You talk as much as you want and the carrier sends you a bill at the end of the month. For this sort of service, expect that you’ll need to provide a credit card number that will be kept on file, pass a credit check, and if you’re renting, possibly pay a deposit of $150-$200 (the fee will be put on your credit card and released when you pay the bill).
With a prepaid SIM card, you purchase a set amount of credit, and each time you make a call the charges are deducted from your credit balance. When your balance is exhausted you can purchase additional credit, often from the provider’s or retailer’s website, or by calling customer service if you don’t have Internet access.
Prepaid cards help you keep track of your budget. Neither type of card invariably offers the best bang for your buck as call rates vary widely so check around for a plan that suits you.