A lot of KSAT viewers and online posters took to the comments section of a Defenders' story and to the KSAT Facebook page, expressing their frustration in the wake of a recent credit card surcharge story.

In Texas, it is illegal to charge a fee for using a credit card, and yet very few customers or businesses realize it.

The Defenders uncovered that a state law prohibiting the charges isn't new, but having an agency designated to enforce it is. The law also now applies to debit cards as well.

"I have been aware of this for some time and it had saved me money," said viewer Rob Lopez. "In this bad economy, businesses will try every method to get your hard-earned money. Knowledge is power."

The Defenders also discovered that government entities are exempt from the law. They are allowed to tack on a credit card surcharge.

And while a business cannot charge a credit card fee, they can set a minimum charge for using credit cards.

"If businesses are not allowed to change the fee, then the cash customers are also paying for the credit card costs because it has to then be figured into the price," said a poster who goes by the handle "crattrasher."

Many viewer comments concerned an additional fee that CPS Energy charged its customers.

"CPS charges $2.50 to use a credit card to pay your bill online," viewer J. Manuel Valer said. "Is this the same?"

A company spokesman said CPS Energy explained that they use Chase Bank for third-party billing and it is Chase that is charging the fee.

To read more about the law, click here.

For a list of recent stories April Molina has done, click here.