Responding to years of complaints over customer service and billing practices by cable and satellite-TV companies, the U.S. Senate Permanent Subcommittee is poised to release its findings from a year-long probe into the industry, Sen. Claire McCaskill (D., Mo.) and Sen. Rob Portman (R., Ohio) announced on Thursday.

The subcommittee - which also has investigated human trafficking and a U.S.-funded counternarcotics program in Afghanistan - subpoenaed documents from pay-TV companies and solicited comments on customer experiences.

The subcommittee's bully pulpit will shine a bright light on industry practices. But solutions will have to be enacted through legislation on Capitol Hill or the Federal Communications Commission.

Comcast, one of the companies investigated along with Time Warner Cable, Charter Communications Inc., DirecTV, and Dish, had no comment on Thursday.

Officials with the companies are expected to testify on June 23 in Washington, a subcommittee spokesman said.

"Consumers in every corner of the country share common experiences about fending for themselves against customer service and billing practices by TV providers that are at best confusing, and at worst deceptive," McCaskill and Portman said in a statement.

"For more than a year, we have conducted a bipartisan investigation of the largest cable and satellite-TV companies. We believe our hearing will be a big step forward for consumers, allowing them to understand how their TV providers really work and make informed decisions about their video service," they added.

Portman is the chair and McCaskill is the ranking Democrat of the subcommittee, which solicited consumer input last year.

Time Warner Cable is a major pay-TV provider, which includes high-speed internet, in Missouri and Ohio.

Customer backlash against cable-TV operators crested when Comcast announced plans to acquire Time Warner Cable for about $45 billion in 2014. Both companies had some of the worst customer service satisfaction ratings of any U.S. company or brand.

The subcommittee subpoenaed customer service and billing data from the pay-TV operators over the last year and spoke with company officials, industry sources say.

Comcast has acknowledged poor customer service, and in 2015 agreed to hire 5,000 call center representatives and technicians.

The latest American Customer Satisfaction Index, released June 1, showed that Comcast improved its satisfaction ratings over the last year, but they remained low.

Comcast's internet service ranked sixth from the bottom of about 340 companies or brands. The Xfinity pay-TV service ranked 11th from the bottom.

The 62 score for Comcast's TV service is roughly a return to its 2013 score, which was 63.

ASCI L.L.C., a for-profit research company spun out of the University of Michigan and based in Ann Arbor, Mich., produces the index. Its telecom ratings were based on 13,000 customer surveys in March and covers pay-TV, high-speed internet, wireless carriers, cellphone manufacturers, and landline phone service.

The June 23 hearing will be held at 10 a.m. in Washington's Senate Dirksen Office Building.