The Federal Communications Commission proposed $11.7 million in penalties against four companies that allegedly charged thousands of customers for long-distance services without authorization — known as “cramming.”

The companies — Main Street Telephone, VoiceNet Telephone LLC, Cheap2Dial Telephone LLC and Norristown Telephone — are accused of adding “dial-around” long-distance service to customers’ bills, which bypass a customer’s normal long-distance carrier. Such services often require a customer to dial an access code that often begins with “10-10.”

The agency Enforcement Bureau’s investigation of the companies found that only a one-tenth of one percent of the affected customers actually used the services for which they were charged over a period of months and sometimes years.

Addressing the trend of cramming, the commission has released an advisory warning customers about the practice and promising to aggressively enforce rules banning it.