Updated: 10/11/10 4:55 p.m.

CHICAGO (CBS/WBBM) – If you use a cell phone, chances are you’re wasting money. That’s according to the Citizen’s Utility Board, which came to that conclusion after studying thousands of cell phone bills.

LISTEN: Newsradio 780’s Mike Krauser Reports

CUB analyzed 4,400 cell phone bills for an entire year. It found that two-thirds of customers are paying more each month than they should be. Illinois cell phone users are throwing away as much as $900 million a year combined.

“Illinois consumers are grossly overpaying for cell phone service. The average consumer is overpaying over $300 a year,” said CUB Executive director David Kolata.

CUB found five mistakes that cause consumers to overpay. At the top of the list: paying for minutes you never use.

“Certainly one of the biggest problems is wasted minutes,” Kolata said. “The bottom line is that most consumers are paying for far more minutes than they actually use.”

The average person, Kolata says, has up to six hours of unused calling time each month. That means they’re on the wrong cell phone plan.

Adrian Garza says he pays for 600 minutes per month, but only uses 100. Another customer is paying for 450 minutes a month, but only using 254.

“This is a person who might be better suited for a prepaid cell phone plan,” said CUB analyst Patrick Deignan.

If he pre-pays for 250 minutes at 10 cents a minute, he’d save about $25 a month: cutting his monthly bill in half.

Mistake number two: not catching billing errors.

“They bill you for the web and you ain’t even got the Internet,” said Cecilia Nichols.

That’s the $2 data charge you may see. CUB says wireless companies have also been known to charge you, even when you have free nights and weekends.

“You want to read your bill, go over it line by line,” said Kolata.

Mistake number three: you don’t need to pay for Directory Assistance.

CUB suggests you get it free with 1-800-GOOG-411, 1-800-INFO-FAST, and 1-800-FREE-411.

Mistake number four: $3 a month for Roadside Assistance may be unnecessary. You’re probably covered with AAA or your car insurance.

And mistake number five: monthly phone insurance, about $5 a month, may not cover what you think.

“You might drop the phone in the toilet or in the sink, or in the tub. In a lot of cases, that’s not covered,” said Kolata.

Kolata says unnecessary extras, like insurance and roadside assistance cost the average cell phone user about $100 a year. Unless you have a really expensive phone, he says insurance is probably not worth it.

You can use CUB’s “Cellphone Saver” service to find out if you’re paying too much.

“What the Cellphone Saver does is it analyzes the calls you make and the data that you use, and recommends the best plan for you,” said Kolata.

To use CUB’s Cellphone Saver, click here.

CBS 2’s Mike Puccinelli and Dorothy Tucker, and Newsradio 780’s Mike Krauser contributed to this report.

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