Confusing cell phone bills, policy statements and fees could become more understandable, preventing the shock from higher-than-expected charges on your monthly bill.

About 30 million Americans, or one in six, have experienced what’s known as “bill shock” caused by an unexpected increase in monthly cell phone bills, according to a new study by the Federal Communications Commission, which plans to work with wireless carriers and consumer groups to help prevent the problem.

According to the agency’s survey of 3,005 American adults, 84% of cell phone users who experienced bill shock said that their carrier didn’t contact them when they were about to exceed their limit on minutes, text messages or data downloads before racking up more expensive additional charges. More than a third of those who experienced bill shock saw their bills go up at least $50, and 23% said their bills went up by $100 or more.

What’s more, 18% of those surveyed didn’t know whether they were subject to an early termination fee for breaking their cell phone contract and, of those who did, 47% didn’t know how much they’d have to pay.

The FCC already has truth-in-billing rules that require carriers to clearly list charges on their customers’ bills, but some carriers have worked to make them more understandable, according to a report from the U.S. Government Accountability Office.

Earlier this month, CTIA, a wireless industry trade association, outlined ways consumers can manage their cell phone use including ways to check your balance and minutes used via text message.

Additionally, in order to avoid bill shock, cell phone users should make it a point to understand voice calling, texting and data usage habits including when, where and who they call, the FCC advises.

If you have a family plan, know what each member’s usage is like, the FCC suggests. All too often, parents can be shocked by how frequently their children text. And you can always ask your carrier what kind of plan would be best for you.

Roaming charges can add up as well, so find out where they occur and how much they’ll cost you, the FCC says. And if you don’t use your cell phone often, consider a prepaid plan to prevent overages.

Does your kid spend too much time and money sending text messages? Check out our article on crazy teen texters.