WASHINGTON » When a mysterious, unauthorized fee appears on your cellphone bill, it’s called "cramming" and consumer advocates and regulators worry it’s emerging as a significant problem as people increasingly ditch their landlines for wireless phones.

The cramming fee is bogus and usually small, under $10 a month. It might be listed on your bill as a "premium service" or other generic-sounding charge. Cramming had long been a problem with traditional landline phones, but after pressure from lawmakers, regulators and others, some of the largest landline carriers last year said they would no longer allow third-party billing — where an outside company offers and then charges the landline customer for services like third-party email, faxing, and voicemail.

Now, the focus of concern is shifting to wireless phones and cramming.

"As people continue to use mobile phones as a payment option, this problem is likely to grow," says Malini Mithal, an assistant director in the financial practices division at the Federal Trade Commission. "It’s just a new opportunity for fraudsters."

The commission held a daylong conference on the issue Wednesday with consumer advocates, wireless carrier representatives, and state and federal officials. The meeting came just weeks after the FTC lodged its first mobile cramming case, accusing a Georgia-based company, Wise Media, of bilking consumers out of millions of dollars for text messages with horoscopes, flirting tips and other information.

According to the agency, consumers across the country were signed up randomly for text services from Wise Media and charged $9.99 a month on their mobile bills, without their knowledge or permission. The text messages suggested people had subscribed to the service, but many consumers dismissed the texts as spam. People who responded and said they didn’t want the service were charged anyway, the agency said.