The U.S. Justice Department has concluded an investigation into the rates major cell service carriers charge customers for text messages and concluded that the companies didn't work in concert to force higher prices on customers, according to the Wall Street Journal.

The DOJ had been investigating whether or not AT&T, Verizon, T-Mobile, and Sprint Nextel carriers colluded to raise per-message SMS fees over a three year period.

"The four companies increased their text messaging prices in two steps -- first from 10 to 15 cents, and then from 15 to 20 cents—within months or weeks of each other," said chairman of the Senate Antitrust, Competition Policy and Consumer Rights subcommittee, Senator Herb Kohl (D, WI).

He added that the rate increases happened even though the cost for the carriers stayed below a penny per message.

While the investigation into whether or not cell carriers worked together to artificially inflate the price of text messages has ended, the Government is still looking into the practice of offering specific cell phones through exclusive carrier deals.

The FCC is currently investigating the impact on competition exclusive carrier deals may be having on the market and whether or not they're fair to consumers.

Exclusive deals are common in the United States. AT&T's iPhone deal, and Verizon's Droid deal are just two of the high-profile exclusive carrier deals customers are currently faced with.

The FCC hasn't said how long it expects its investigation to take.