The U.S. Federal Communications Commission announced on Wednesday that it could fine AT&T $100 million over allegations of misleading customers about unlimited data plans. The U.S. wireless carrier reportedly "throttled" or slowed down the Internet speed of their users without informing them.

"Consumers deserve to get what they pay for," FCC Chairman Tom Wheeler said. "Broadband providers must be upfront and transparent about the services they provide. The FCC will not stand idly by while consumers are deceived by misleading marketing materials and insufficient disclosure."

The agency found that once the users experienced a significantly slower Internet speed once they reached a certain amount of data used. In most cases, users can no longer stream videos or use their GPS since they are only able to use 5 percent of their expected speed. This problem lasts for an average of 12 days per billing cycle, according to the New York Times.

The FCC accused AT&T of throttling its customers' unlimited data plans since 2011 without disclosing it, thus violating the 2010 Open Internet Transparency Rule. The company quickly disagreed with the allegations, saying that the agency approved this practice for all major carriers, according to BBC.

"The FCC has specifically identified this practice as a legitimate and reasonable way to manage network resources for the benefit of all customers, and has known for years that all of the major carriers use it," AT&T said in a statement.

"We have been fully transparent with our customers, providing notice in multiple ways," the wireless carrier added, pointing to a notice posted on its website.

The customers will not receive a single cent from the $100-million fine since it will go to the U.S. Treasury, the Los Angeles Times reported.

Aside from the penalty, the FCC is expecting AT&T to correct its misleading advertising and compensate the affected customers.