Shapiro has long used her credit-card statements as an accounting tool. She color-codes each item, and pays some expenses from a separate checking account. Her May statement said she owed $2,435.46. Her payments added up to $2,435.21.
In other words, she was 25 cents short. But that was enough to trigger a monthly interest charge, based on the bank's calculation of her average daily balance for the entire month. So her next statement said she owed an additional $18.25.
Shapiro contacted the bank to question the charge, which seemed unfair for an obvious error. Instead of what she expected - a waiver of the interest, as a courtesy - she got pushback. "They just tell you, 'Well, it's your mistake, not our mistake,' " she told me last week.
After what seemed like a whole morning on the phone and a visit to a branch, she got some satisfaction. The bank promised to reconsider the charge.
And, sure enough, there was a credit on her next statement for the $18.25 - along with a new interest charge of more than $21.
Why? Because, again, she hadn't paid her entire balance. She'd withheld the disputed $18.25 from her otherwise-in-full payment of more than $1,900.
I wish I could say here that the bank, soon to be renamed Santander for its Spanish parent, concedes it was silly to anger a good customer for $18. Shapiro keeps sizable savings in the bank. And she uses her Visa credit card regularly - or did, until she got fed up. "Lately, I've been carrying around my checkbook and paying by check," she says.
That it was needlessly discourteous may, in fact, be Sovereign's internal conclusion. But all vice president Mary Ellen Higgins would tell me was that the bank was willing to look further into the dispute. "We don't discuss our clients' business with the media," she says.
Shapiro was irked enough to complain publicly - all the more so after polling a handful of friends and finding two who faced similar charges for similarly minor shortfalls.
To Shapiro, the practice seems like a scam. "If someone owes you 25 cents and you can get $18 from it, you might as well be walking around with a gun on the street," she says. "It's a sleazy way to make money."
Although the practice that caught Shapiro is disclosed in Sovereign's terms of service, some consumer advocates have long agreed, and pushed for Congress to outlaw what's known as "trailing" or "residual" interest during 2009's credit-card reforms.
Complaints more commonly arise from consumers who knowingly fall short of paying their full balance, say, by $100, without realizing they'll owe interest on a much larger amount, partly because carrying a balance means losing benefit of the so-called grace period on new purchases.
Card issuers have long argued that charging interest on a whole month's average daily balance compensates them for those who pay in full, sometimes derided as "free riders" on the pay-with-plastic train. Of course, that portrayal ignores the 2 percent or more that banks take off the top of each purchase.
But let's get back to Shapiro, who wasn't knowingly carrying any balance at all.
Linda Sherry, of Consumer Action, says what's likely obvious: "When it's 25 cents that we're talking about, that's obnoxious." But she also suggests that the bank should have treated Shapiro's complaint as a dispute under the Fair Credit Billing Act, which allows cardholders to withhold payment of a disputed charge while details are weighed.
In this case, I'm wagering that Sovereign would have benefited, too. Chances are it would have chosen to forgo nearly $40 in gotcha interest. But penny-wise and pound-foolish is rarely the right way to go.
Contact Jeff Gelles at 215-854-2776, email@example.com, or @jeffgelles on Twitter. Read his blog at www.inquirer.com/consumer.