In an extreme example, an Illinois man racked up a $27,000 bill from AT&T for streaming a Chicago Bears game from his laptop while on a Caribbean cruise.
Using his laptop, a wireless card and Slingbox device that let him watch the game via an Internet connection, he tuned into watch the Bears battle the Detroit Lions.
But, charging him by the kilobyte, at the international rate, the company said he was roaming for the three hours it took to watch the game.
The man dug up the documentation to prove that he was not at sea but actually in port at Miami when he was watching the game, but the company stood firm. Even after he pled his case to 14 different employees, they would only reduce the bill to $6,000.
Ultimately, however, after the Chicago Sun-Times ran his story and brought his case up with AT&T, the company dropped the charges.
Ringtones, wallpaper, games. Sometimes you want them on your cell phone, sometimes you don't. But consumer advocates caution that fees charged by the third parties that sell those products to the consumer and then collected through the cell phone bill are another problem.
In some cases, the fees end up on the consumer's bill through misleading means. A scam wending its way through Facebook earlier this year tricked users into signing up for a cell phone service by asking them to provide their cell phone numbers to receive the results of an online IQ test.
Typing in their cell phone numbers unwittingly signed them up for cell phone services that started at $9.99 a month. But getting those charges off a cell phone bill is no easy task.
"They're having a huge economic benefit from it," said UCAN's Neill, adding that removing the charges is "more difficult than it should be. They ultimately control the phone bill."
Teenagers are an easy target, he said, as they might not even know that a certain download or game will result in a monthly charge.
For their part, cell phone companies say that they have implemented safeguards to protect users.
An AT&T spokeswoman said that when customers are considering purchasing downloadable options, such as ring tones, wallpaper, games or other content, they must opt-in twice -- and take two actions -- to indicate that they want to receive the services. Third-party providers must make pricing and directions for unsubscribing clear to users, the spokeswoman said.
If customers want to dispute charges, AT&T said it reviews complaints and makes billing adjustments on a case-by-case basis.
A spokeswoman for Verizon Wireless said that it has similar safeguards and reviews billing issues as they arise with customers.
If you go out and buy the new iPhone 3GS, it will cost you $199 (if you get the 16 GB version). But AT&T buys the phone from Apple for $400.
Like many carriers, AT&T entices customers with lower-priced or free phones if they agree to a two-year contract (depending on the carrier, the contract term could be different).
But it turns out it's not such a sweet deal after all.
"One of the biggest [issues] are these free and discounted phones," said Consumer Reports' Blyskal. "We've done work that shows those phones, you actually pay for them. It's built into the service charge."
So though you pay $200 initially, you pay the remainder each month with your service bill. But even though you eventually pay off the phone, your monthly bill never goes down.
ABC News' Elisabeth Leamy contributed to this report.