There are some people who, for a variety of reasons, may not be interested in locking themselves into a contract. There are undeniable reasons for having a cell phone available, whatever a person's reservations. One reason for using prepaid plans is to keep a cell phone in case of emergencies. In a case like this, a prepaid phone card or phone can be purchased--usually for a relatively small amount of money--and kept someplace like the glove box of a car.

One of the downsides of a prepaid cell phone is that the minutes, although they're already paid for, can expire after a set amount of time. Sometimes this will be as little as 30 days, and at other times as long as six months. It's important, therefore, to remain mindful of the minutes and either use them or re-up them, as the case may warrant.

Sometimes, prepaid cellular plans involve the purchase of a prepaid SIM card, either in addition to or instead of a phone. SIM stands for 'subscriber information module,' and it's essentially the 'brain' of a cell phone. This card will have the salient information about the user. When a regular cell phone user upgrades phones, the SIM card will be put in the new phone, and the address book and other personalized information will move from phone to phone.

When purchasing prepaid SIM cards, it should be pointed out that a person cannot purchase a card and put it into every phone. The phone in question must be 'unlocked.' A SIM card can be used, for example, when traveling to a foreign country, with a prepaid phone card purchased for use in that country. A phone will likely have to be purchased at the same time, especially if that person already has cellular service in the United States, since the SIM card probably won't work in the phone of a major provider.