by KYW's John Ostapkovich

As airlines add fees and decrease service, some people looking to cash-in on credit cards that offer frequent flyer miles are getting less than they bargained for.

It used to be a better deal, join a frequent flyer program and use a credit card that added miles to it as you bought stuff and pretty soon you'd be on your way somewhere free. Well, now it's less free with fees and higher mileage requirements in some cases.

The problem with air miles cards, and all rewards cards, says Philadelphia's consumer advocate Lance Haver is that the deal can change to your detriment:

"It's very difficult to believe that the terms that you're offered today are going to be the terms you can use six months or a year from now as fuel goes up and the economic environment changes."

Haver says, if you pay the card balance every month, maybe a rewards card makes financial sense but you don't shop for a better interest rate, not a better gimmick, to keep a little more of your money.