By Brendan Sasso - 07/18/13 08:40 PM EDT
The lawmakers all serve on the House Energy and Commerce subcommittee on Communications and Technology, and Eshoo is the panel's ranking member.
Verizon, AT&T, Sprint, T-Mobile and CenturyLink received the letters.
The lawmakers asked the companies to detail any extra fees they charge and how they disclose those fees. They asked whether the companies charge customers for changing their service plan and whether they notify consumers before imposing extra costs.
Jot Carpenter, the vice president of government affairs for wireless industry group CTIA, said the mobile carriers "do an excellent job in disclosing taxes, fees, and other charges to consumers" and are bound to follow an industry code of conduct.
He noted that the carriers already agreed two years ago to provide alerts to consumers before imposing additional fees for surpassing limits on voice, text, data or roaming.
—Updated at 5:22 p.m.