More than a year ago, Teresa Dixon Murray says she started to feel something wasn't right about her family's Verizon Wireless cell phone bill.
"I was getting $1.99 charges on usually two out of my three accounts," said Murray, a reporter with the Cleveland Plain Dealer and the mother of two teenagers with cell phones.
She said that her family was being charged for Internet use but no one was using the Internet. The mystery charge even appeared, she said, when one of her sons' phones was locked away after he'd lost phone privileges.
"I knew absolutely, positively for sure. No accidents. No excuses, that this was wrong," she said. "And I was absolutely livid."
After months of complaining to Verizon, Murray wrote a newspaper column. After that, she got the company's red carpet treatment and her money back. Her situation was settled -- but thousands wrote to her saying that they'd had the same problem.
Now thanks to a Federal Communications Commission investigation into Verizon Wireless, some of those customers could see credits of $2 to $6 on their October or November bills.
Last year, the FCC questioned Verizon Wireless about a $1.99-a-megabyte data access fee that had appeared on the bills of customers who didn't have data plans but who had accidentally initiated data or Web access by pressing a button on their phones.
Verizon Wireless said that it had stopped charging such fees when a customer started using a data service and then shut it off quickly. It blamed the continued overcharging on a software glitch and has agreed to pay up to $90 million in refunds to affected consumers.
The FCC said Sunday that it had been examining the charges after consumers' complaints.
"We're gratified to see Verizon agree to finally repay its customers," FCC Enforcement Bureau Chief Michele Ellison said in a statement.
Verizon Wireless said in a statement Sunday that most of the 15 million customers who had been overcharged would receive credits -- some could get more than $2 to $6. Customers no longer with the New York-based carrier will get refund checks.
"Verizon Wireless values our customer relationships and we always want to do the right thing for our customers," said Mary Coyne, deputy general counsel for Verizon Wireless, according to The Associated Press. "The majority of the data sessions involved minor data exchanges caused by software built into their phones; others involved accessing the Web, which should not have incurred charges. We have addressed these issues to avoid unintended data charges in the future."
Former cell phone executives at the consulting firm Validas said that consumers have to go over their cell phone bills with a fine-toothed comb.
"The carriers have 50 [million], 60 [million] or 90 million customers and they charge everybody every month a few extra bucks," said Ed Finegold, Validas' chief analytics officer. "That adds up to billions in profits for them, so they have every incentive in the world to do it."
Here are some fees that may be red flags and should be looked at closely:
Download charges you don't recognize.
Charges for nights and weekends when you signed up for them to be free.
ABC News' Lisa Stark and Brian Hartman and The Associated Press contributed to this article.