They're legal but they're sneaky.  So-called "grey charges" are a way for some companies to make big bucks.  In fact, experts say one in four consumers are paying them.  Travel blogger Kim Orlando was one of them.

Orlando writes and tweets about her many adventures.   To make life on the road easier she paid a company for a trial subscription to track reaction to her tweets. 

"I thought I was going to pay $149 for that one month," she said.

But instead,  Orlando says she was billed four months in a row, something she says never signed up for, and she points to an email from a company rep as proof

"I thought well this is fishy," she said.

Experts say a "trial subscription turned permanent" is just one type of "grey charge."

"Grey charges are unwanted sneaky little charges that are, that are starting to show up on consumers' credit statements and bank statements," explained financial expert Jeffrey Cutter.

How do businesses get away with it?   A survey found eight out of 10 people merely skim their credit card and bank statements.

"I'm embarrassed to say that it took me four months to figure out I had been billed every month," admitted Orlando.

Other grey charges include "unknown subscriptions."  That's when you make an online purchase and forget to click or unclick one little box, so you end up opting in for another purchase.

 "Over the past half a year we have seen more and more of these charges," said Cutter.

Another charge could be what's called " zombie subscriptions." Say you cancel a gym membership or a magazine subscription, sometimes a few months later the charges come "back from the dead."   

One more creepy charge is the "cost creep," where a monthly subscription slowly increases in price. Many grey charges are legal if businesses spell them out in those "terms and conditions" most of us also just gloss over.

"Make sure when you are purchasing anything, or that you read everything and understand exactly what you're doing; that's partially your job," said Jerry Cerasale with the Direct Marketing Association.

But federal regulations require that offers be "clearly and conspicuously" disclosed.  The Federal Trade Commission says it's definitely getting consumer complaints about grey charges.  

The Direct Marketing Association says sometimes there are misunderstandings, but admits other times companies just don't follow the rules.  

"There are bad actors, but don't let that stop you. Trust the good marketers," said Cerasale.

Orlando challenged her grey charges, but says the company insists she signed up, so it's now in dispute with her credit card company.    

The Direct Marketing Association and Federal Trade Commission have taken action against companies who charge consumers without properly disclosing the conditions of an offer.  If you feel you've been unfairly charged, report it.