Senior House lawmakers on Wednesday sought help from some of the country's biggest phone companies to investigate what the companies say are abuses of costly connection charges in rural areas.

AT&T Inc. (T), Verizon Communications Inc. (VZ), Sprint Nextel Corp. (S), and Qwest Communications International Inc. (Q) all have accused some small phone companies of taking advantage of high connection rates by partnering with adult chat lines or free conference call centers to drive more phone traffic through their systems.

The issue has caught fire in the wake of recent disclosures that Google Inc. (GOOG) is blocking those expensive calls through it's Google Voice phone management service. Google has the highest profile of Internet companies offering phone services engaged in call blocking.

House Energy and Commerce Committee Chairman Henry Waxman, D-Calif., sent a letter to Verizon, Sprint, AT&T, and Qwest letters Wednesday asking for details about their disputes with rural phone companies over inflated call volume to high-cost areas.

Telecommunications Subcommittee Chairman Rick Boucher, D-Va., and Oversight Subcommittee Chairman Bart Stupak, D-Mich., also signed the letter.

Other lawmakers representing rural areas have said blocking calls to high-cost numbers could hurt their constituents.

The Iowa Utilities Board recently found that eight local phone carriers had engaged in a practice designed to increase access charge revenues by 10,000% using free adult chat lines.

Large phone companies cheered the Iowa board's decision, while the rural carriers said the board overstepped its jurisdiction. The Federal Communications Commission is reviewing the board's decision.

The call blocking issue appears ripe for regulation. Two years ago, the Federal Communications Commission has expressly forbidden larger phone companies like AT&T and Verizon from blocking calls to high-cost numbers.

The FCC recently asked Google how its phone service restricts calls to certain numbers and sought input on how Google's new media product should fit within current telecom law.

Waxman's letter said any investigation into blocked calls should also examine "the existing access charge regime and purported abuses of that system."

Large carriers have for years asked the FCC to address practices they dub "traffic pumping." They have also taken their complaints to court, saying rural companies are making a mint off the practice.

Waxman's letter asks the company executives whether they have withheld payment from the smaller rural companies as a part of their legal disputes. The rural companies involved the lawsuits say they are owed tens of millions in unpaid access charges.

Ross Buntrock, an attorney representing the rural carriers, welcomed the letter because he said it acknowledges that his clients aren't getting paid.

"Don't let companies like AT&T and Qwest starve rural carriers out of existence by refusing to play by the rules that exist," Buntrock said, noting that there's nothing illegal about routing calls through high cost areas. Buntrock is with the Washington, D.C. law firm Arent Fox.

Verizon and Sprint both cheered the inquiry from Waxman and his colleagues. "We welcome any effort to address the harmful traffic pumping schemes that have plagued the industry for the last several years, and we look forward to responding to the questions from members of Congress," said Verizon spokesman David Fish.

Sprint Senior Vice President Vonya B. McCann said, "Excessive access rates are the root cause for many of the industry's problems, including traffic pumping schemes."

AT&T spokesman Michael Balmoris said AT&T is happy to assist the lawmakers in their investigation. "We are especially eager to provide members of Congress with information related to [Internet-based phone] providers who are still blocking calls with impunity," he said.

Qwest Senior Vice President of Public Policy, Steve Davis, said Qwest is pleased to cooperate with the inquiry. "We encourage Congress to make similar requests for information from the companies engaged in traffic pumping," he said.

-By Fawn Johnson, Dow Jones Newswires; 202-862-9263; fawn.johnson@dowjones.com