We all know gas is expensive enough, and the last thing we need is another fee. But that's exactly what's happening to some people who use a debit card.

Melissa Hagan of Johnstown recently used her debit card to get gas. She only put five dollars in, but when she checked her account balance later that day 25 dollars was missing.

"You hear all these reports on the news of identity theft and credit card theft," says Hagan. "That's immediately what went through my mind."

It turns out the extra 20 dollars taken from Melissa's account is part of a practice called a debit card hold. It's allows gas stations to make sure there's enough funds in your account to cover the purchase. "You're pretty much saying we're gonna take your money just to be on the safe side," says Hagan.

Bank officials say the hold will be lifted after a few days, and it could make your account appear to have a negative balance. But they insist you will not be charged an overdraft fee.

But Melissa Hagan fears she may need that money while it's on hold and is already using other means the next time she fills up. "I have not used my debit card for gas," she says. "I would use cash, or I'll write a check, or I'll go somewhere else."

It's not just gas stations. Other merchants can put holds on your money when you use a debit card. Many hotels and car rental companies are already doing it.