Earlier this year, consumers were up in arms over credit card issuers suddenly increasing interest rates on balances or sending out bills just two weeks before payment was due. The public outcry was so great that Congress passed legislation that will rein in the worst of the credit card companies' practices.

Some of those changes take effect this month; other consumer-protection measures will not take effect until early next year. Not surprisingly, credit card companies are doing everything they can before the new rules become law, including adding annual fees and adjusting borrowing limits or interest rates.

As a result of this, and in some cases trying to be more prudent about spending money, many consumers have shifted to debit cards for convenience. But simply using a debit card instead of a credit card does not shield users from abusive business practices.

One of the most troubling is how overdraft fees and penalties work with many, but not all, debit cards. And since banks make an estimated $38 billion from overdraft and bounced-check fees, they are not inclined to make reasonable changes to their business practices unless forced to by Congress. Given that reality, Congress should mandate more consumer protection and transparency for users of debit cards.

Overdraft charges should not even be an issue for debit cards, since the cards are intended to provide access to cash in a bank account, not a line of credit. If not enough cash is available for a purchase or a cash withdrawal, the transaction should be — and at one time was — refused. That no longer is the case.

Nowadays, a debit card transaction that will overdraw a bank account generally is allowed to proceed — with no warning — and then fees and penalties are charged against the cardholder.

A study conducted by the Center for Responsible Lending, and quoted in the New York Times, highlighted one college student who used his debit card to make seven small purhases for school supplies, coffee and other items that amounted to just $16.55. But because he unwittingly was overdrawn on his bank account, he was hit with $245 in charges.

A 2008 study by the Federal Deposit Insurance Corporation found that overdraft fees, which are fixed and escalate with succesive purchases, amount to charging customers 3,500 percent interest, because the amounts of the overdrafts generally are small.

One positive step in curbing debit card abuses by banks would require return to the former system of denying a purchase if inadequate funds are in the account. Still better would be a system that notifies the consumer that the pending purchase or cash withdrawal will cause an overdraft resulting in fees, and spelling out those fees. If the customer wants to, or needs to, proceed with the purchase or cash withdrawal, and incur the fees or penalties, it will be with full knowledge of the consequences.

The current system, which banks defend as a customer service they call "overdraft protection," actually is an abusive system that hits lower-income people hardest. Even without reform, bank customers should fully understand how debit card usage can trigger fees and penalties.

For years, banks had been taking advantage of credit card customers. Public outcry forced Congress to act. Until Congress examines debit card complaints, card users should learn how their bank deals with overdrafts. And if they don't like the terms, they should shop for another debit card and bank with terms that are fair.

It should not be surprising that similar abuses are hitting debit card users. Congress should return to the issue of consumer protection and force greater transparency when it comes to debit cards and fees or penalties charged customers who unknowingly overdraw their bank accounts, even by just a few dollars.

Debit cards are a great convenience, but bank customers deserve to know when a potential purchase or cash withdrawal will trigger a fee or penalty.