The next time you feel like downloading the latest hot single as a cell phone ring tone, listen carefully. That sound you hear may be your wallet deflating, thanks to charges on your bill from services you didn't even know you were buying.

Jamster, a subsidiary of Internet infrastructure provider VeriSign that specializes in custom content for mobile devices, has been accused of defrauding customers into paying for ring tones they didn't authorize, and using deceptive marketing to lure consumers into purchasing its products.

One irate customer filed a lawsuit in San Diego alleging that applying for Jamster's "free ring tones" actually result in receiving "junk text" messages that subscribers get charged for.

The lawsuit alleges that Jamster would promote free downloadable ring tones to any subscriber who registered with its site or responded to the advertisement by sending a text message with a special code.

The subscriber would then receive multiple messages from Jamster stating that its content was available for download. However, the subscriber would be charged for every text message sent from Jamster, at a rate of $1.99 per message plus fees from their wireless carrier.

The lawsuit also names wireless providers AT&T Wireless, Cingular and T-Mobile as defendants. SBC Communications, which owns Cingular jointly with BellSouth, is a Verisign client, as was AT&T Wireless prior to its buyout by Cingular.

"What we're seeing is a lot of people seeing these ads and thinking they can download a ring tone or wall paper for their phone, and suddenly they're signed up for a subscription," said Kate Hartman, one of the attorneys on the case.

Hartman sees Jamster and wireless providers as "using your phone bill like a credit card," automatically charging customers for service without explaining or even identifying what the charges are.

Another problem Hartman identified is that many frustrated customers cancel their plans in order to be rid of Jamster, thus incurring heavy "early termination" fees. Not only that, but phone numbers from canceled contracts are recycled and given to new customers, who suddenly have to contend with charges from Jamster without ever having used or encountered the service.

Consumer Affairs.Com has received several complaints from cell phone subscribers wondering how they ended up with charges from Jamster on their bills.

Leslie C., from Oakland, CA, signed herself and her husband for T-Mobile's Family Share plan, only to find that she received unauthorized charges from Jamster for the first two months.

"It outrages me that a ring tone company can send him ring tones and charge [us] without some action required on his part to accept these charges. These charges were never permitted by myself or my husband and seem completely illegal."

Steve from Cleveland, OH receives multiple text messages from Jamster on his phone each week. "I have tried e-mailing them through their web site but the spamming does not stop. [There is] no tangible damage, just severe annoyance and frustration over the fact that I have no way to stop getting spammed over and over by the same company."

Jamster's terms of service specify that if a user downloads content from the company onto their phone, "yourepresent that you are at least 13 years of age and have the consent of the subscriber of a participating mobile communications carrier to sign-up for and use the Jamster service on behalf of the subscriber," and that the download constitutes an agreement to use its services.

Critics of Jamster contend that the service advertises on teen-oriented television shows and channels such as Nickelodeon and MTV in order to convince young cell phone users to get the "free ring tone."

An online petition entitled Stop is filled with tales of woe from defrauded customers, as well as vitriolic sentiment for the company's ubiquitous "Crazy Frog" ad and ring tone.

"I'm tired of seeing commercials for stupid, useless add-ons for my phone that no one could possibly ever needand I want to kill that stupid frog," fumes one signer.

Not only are Jamster clients irate. Cell phone content provider Jamdat Mobile has filed suit against VeriSign alleging infringement on its trademark.