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The small charges are tucked into bills under innocuous headings such as "additional charges," Swanson said. "This is designed to be under the radar. People don't read their phone bills every month."
Many people incur the charges -- known as "cramming" -- unwittingly. For example, a consumer who is online may click on a pop-up ad offering a store coupon and must allow a text message to receive a PIN for the coupon. The crammer then uses access to the consumer's account to add charges for unwanted things such as ringtones and horoscopes.
No. 1 mobile carrier Verizon Wireless hasn't signed on to the agreement, and it doesn't apply to land lines, Swanson said, so those customers should check their bills.