The Senate will release the findings later this month of a year-long investigation into customer service and billing practices in the cable and satellite-TV industries, Sens. Claire McCaskill, D-Mo., and Rob Portman, R-Ohio, announced on Thursday.

The Senate Permanent Subcommittee on Investigations scheduled a June 23 public hearing in Washington on the pay-TV practices and will release a report on the investigation'sindings.

Comcast was one of the companies investigated along with Time Warner Cable, Charter Commuications Inc., DirecTV and Dish. Officials with those companies are expected to testify, a subcommittee spokesman said on Thursday.

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

Comcast, the nation's largest cable-TV company, had no comment on Thursday.

The Philadelphia company has acknowledged poor customer service and in 2015 agreed to hire 5,000 customer service reps and technicians to improve itself.

"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."

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.

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