When planning a trip abroad your flight, hotel, and car rental reservations usually top the list of things to look into, but there is one more important detail that travelers need to consider – your data plan.

"Make sure you have a data plan involved before you go on that trip," Kennesaw resident Joshua Fair told WSB-TV.

It’s a lesson Fair learned the hard way when he received a bill for $4,433.01 from AT&T.

Fair went on a cruise and did not put his phone in airplane mode. The apps running in the background continued using data as the ship sailed into international waters.

Even though his phone was locked in a safe, he was still using data and getting charged. When the ship returned to Miami, Fair had a text from AT&T.

“I had an alert saying that my phone had exceeded high data usages and they froze my account.” Fair explained.

AT&T customer service told him that because his billing cycle had closed they were not able to backdate his plan to a cheaper rate.

They said he could choose to pay a settlement of $2,000 and the remainder of his bill would be forgiven, but for a student and freelance videographer that was still a big chunk of change.

“It’s pretty frustrating. I’m a college student and $4,000 is as much as my tuition,” said Fair.

WSB-TV consumer adviser Clark Howard says your best bet is to switch to T-Mobile, because you can use it anywhere in the world with unlimited data at no cost to you.

The absolute best way to avoid the high fees: Leave your phone at home.