Louise got the shock of her life when she opened her first cell phone bill.

How on earth could her $19.99 calling plan zoom to more than $300? Clearly a case of inaccurate decimal placement. Or was it?

It took only a few minutes with customer service for Louise to learn the sad truth: Her needs and the dirt-cheap calling plan she signed up for were not even on the same planet. She failed to understand a few important details about cell phone usage, or more accurately, wireless communication. And now she's stuck with a one-year contract.

Louise is not alone. Most cell phone users know more about the cool features on their phones than they do about roaming charges, air time allotments or home calling areas.

Wireless phone. Any phone that transmits signals through the air without a physical connection.

Minutes. In wireless speak, minutes mean air time-actual time spent talking on the cellular phone. In the U.S. you rack up air time whether you place or receive the call. The air time meter runs even when you place toll-free calls or calls to directory assistance. The only exception: 911 calls.

Anytime minutes. This is the air time included in your particular plan that you can use anytime of day or night during the month. Unless your plan includes a "rollover" provision, if you don't use your minutes you'll lose them. Louise learned that her $19.99 plan included only 150 minutes of air time. Each minute of air time over cost her $.49.

Home calling area. This is defined by your service plan. If you make or receive a call outside the boundaries of your home area, expect to be charged long distance and or roaming fees on top of air time. Louise had no idea her particular home calling area was so limited.