Consumers have every right to dispute charges on their monthly credit card statements. The law says so. Banks say so on their statements. But doing so is "a royal pain in the tail," a Los Angeles lawyer says.

Indeed, a couple questioning a $26.13 charge from a corporation they never heard of got contradictory information from four different customer service representatives at their own bank. There was some disagreement over whether they had to write the bank, considerable disagreement over whether the disputed charge could be removed so that not paying it would not subject the rest of the bill to finance charges and total disagreement over whether such finance charges would be reapplied when the matter was settled.

Worse, what one is told sometimes seems irrelevant. A New York executive whose Visa card was stolen last summer was forgiven the fraudulent charges, but not before they triggered finance charges. Since then, and despite her numerous notes, the finance charges on those finance charges have been piling up, seemingly unstoppable.

Some 75 million U.S. consumers now charge more than $200 billion a year on their 200 million bank cards. The cards have obvious advantages, including the neat monthly record of purchases and the chance to withhold payment on anything undelivered or unacceptable.

But there can be problems. Bank cards are actually a rather difficult product that leave many people feeling helpless. No descriptive receipts come with the bill, not paying in full kicks off a retroactive loan that can go back two months and finance charges are applied according to variable and incomprehensible formulas that very few consumers understand.

There are even unexpected dangers. An unfamiliar name appearing on a bill could be a business billing in the name of its owner corporation -- a confusing practice prohibited by the operating rules of both the MasterCard and Visa associations. It could also indicate a credit card receipt "laundering" scheme, in which some disreputable business (often, these days, a telemarketing firm) gets card-holders' account numbers, then contracts with a legitimate (if greedy) business to bill them for inferior goods or fictitious purchases. Many consumers, apparently, pay without question.

The applicable regulations are also difficult. Consumers must figure out whether they have a billing error (wrong charge, wrong item, something not delivered) or a dispute over the quality of goods or services purchased. If the problem is a billing error, they must file their dispute within 60 days, wait up to 90 days for their bank's "reasonable investigation" and need not pay the disputed charges or related finance charges during that time.

If the charge was theirs, they must pay up, and banks can (but rarely do) tack finance charges onto that amount. But whether the consumer was right or wrong, finance charges cannot be applied to any undisputed amounts if withholding the disputed amount was what kicked off the finance charge: Someone with thousands in charges who paid all but a disputed $20 should not pay interest on all his purchases because he was $20 short of full payment. It would "discourage people from disputing charges at all," said Nessa Feddis, federal counsel at the District-based American Bankers Association.

The third difficulty is the dispute procedure, involving not just the consumer and merchant, but also the relentless computer and several intermediaries concerned about monies they have already advanced. The "reasonable investigation" required of the card-holder's bank often involves just sending the charge back to the merchant, who in turn sends the charge slip. If the consumer disputes its validity, back it goes again to the merchant, who can still refuse the "charge-back," at which point the card holder is told to pay up.

What's more, bank service representatives do not always understand the procedure themselves. They may not tell card holders they have to write, said Gerri Detweiler, education coordinator at Bankcard Holders of America, a Washington-based consumer group, and "later, the issuer can say 'Sorry, you didn't put it in writing.' " They may tell consumers that they cannot dispute charges already paid (although they can), or may give them, erroneously, the rules for asserting a quality dispute (telling them, for example, that they must first try to resolve the dispute directly with the merchant).

Many, Detweiler said, press the consumer "for irrefutable proof that he is right," when they should be pressing the merchant for his proofs. And when the merchant insists that the charge is valid, it's over: "The bank's whole 'resolution' is the merchant's word," said Elgie Holstein, director of Bankcard Holders.

Finally, it is difficult to find help if one's bank seems unhelpful. The only other way to "rattle the cage of a multimillion-dollar credit card operation is to go to their regulator," Holstein said. But it is not easy, given nine different authorities over credit card issuers, including the Office of the Comptroller of the Currency (national banks), the Office of Thrift Supervision (savings and loans) and the Federal Trade Commission (retailers, oil companies, nonbank card issuers).

Because these agencies must grapple with more weighty stuff than a single questionable charge on a consumer's bill, they may at best offer explanations of procedure, maybe even a little mediation, but rarely resolution. At worst, they just take written complaints, thus adding yet another complaint procedure to one already difficult.