Get out your cable bill now right now and review it. Are you paying for a set-top box, modem or other piece of equipment you don't use or even have? If so, call your cable company right now.

Get out your cable bill and review it. Are you paying for a set-top box, modem or other piece of equipment you don't use or even have? If so, call your cable company right now.

A recent investigation by the U.S. Senate, sponsored in part by Republican Sen. Rob Portman of Cincinnati, found large cable companies nationwide routinely overcharged customers for equipment. Some refused to refund most of the money they'd overcharged.

For example, Time Warner Cable told the Senate it overbilled 40,193 Ohio customers a total of $430,393 in 2015. During the first five months of 2016, the company overbilled customers in Ohio for 11,049 pieces of equipment, totaling $108,221.

Cable giants, including Time Warner, also admitted they made no effort to trace equipment overcharges unless customers specifically asked. In other words, if you don't call to complain, they aren't going to look to see if you're overpaying. The sooner you call, the better.

The Senate investigation examined how Charter Communications, Comcast, Time Warner Cable, DirecTV and Dish Network-which, combined, serve about 70 percent of U.S. cable and satellite customers-handled overcharges and refunds. Other smaller local providers, such as WOW, weren't analyzed.

The survey found Charter and Time Warner were the least likely to refund overcharges and rarely, if ever, refunded the entire amount overcharged. Usually, they only refunded one month of charges.

This is big news in Columbus. Charter doesn't serve central Ohio customers, but it recently merged with Time Warner, which does. Comcast and DirecTV had policies in place to automatically refund credits for overcharged customers for the entire amount (not just one month), and Dish said its billing system is designed to prevent overcharges from occurring at all.

Cable giants came under fire during recent Senate hearings for other consumer-unfriendly practices as well, such as luring customers in with rock-bottom promotional pricing, then not telling them how much the service would cost once the promotion period ended.

They also were taken to task for frustrating customer-service experiences. If you've ever called to cancel service or ask for a lower price and felt like you were getting the runaround, you weren't imagining it. The Senate investigation confirmed what we all suspected: The representative on the other end of the line has been "specifically trained and financially incentivized to prevent the customers from canceling and downgrading," the report said.

"Customers who called for help on their accounts face agents whose job it is not just to solve the customer's problems, but to sell them additional services," said Sen. Claire McCaskill (D-Missouri) at the hearing. "These agents are compensated, in part, based on their ability to sell you more."

It's not just working people who fall victim. Listen to a recording of McCaskill's own comically bad customer service call with her cable company at mccaskill.senate.gov/pay-tv.

Cable and internet providers routinely receive low scores for value and customer satisfaction. In Consumer Reports' latest telecom service ratings, about 30 percent of customers were satisfied, yet only 17 percent dropped or cut back on cable TV in the past year. Why? It's getting harder and harder to ditch your provider, because even those who cut the cord usually still want and need home internet access.

If you're concerned about your bill, the only option is to keep calling, be steadfast and take your business elsewhere if you suspect you're being overcharged. In the meantime, there's a slim silver lining. As a result of the Senate's inquiry, cable giants including Time Warner have agreed to refund overcharges to thousands of customers and improve their customer service.

-Denise Trowbridge is a self-professed money geek who writes about personal finance, banking and insurance for The Columbus Dispatch, bankrate.com and middlepathfinance.com.