She was "shocked," she says, to learn her $39.99 month bill had soared to $476.
Nguyen and her son, Quincy Hoang, an attorney, figured AT&T Wireless had made a billing error.
But, as Hoang says, it wasn't a mistake.
"We were basically told, 'Well, we informed you in a little clause in the statement, the prior month or the month before that,'" says Hoang.
With collection agencies coming after her, Nguyen decided to sue. But she then discovered her contract said she couldn't go to court and had to use binding arbitration.
"The courts are there to ensure fairness," says Hoang. "With arbitration, you don't get all the protections of the courts."
In the past decade, the fine print in almost every contract a consumer faces has a clause requiring binding arbitration. Cingular, which has taken over AT&T Wireless, insists arbitration serves consumers.
"It's fair, it's fast, and oh, by the way, because arbitration would typically take weeks; litigation months or years," says Mark Siegel of Cingular.
In arbitration each side presents its case to a neutral arbitrator whose decision cannot be appealed. Since arbitrations are confidential, it's hard to tell how consumers fare.
"For competitive reasons and legal reasons we do not release the number of cases we handle or their disposition," says Siegel.
Among the few statistics available are those obtained in a lawsuit against credit card giant First USA. Of more than 19,000 arbitrations for debt collection, consumers won just 87 cases.
A more recent, but small study for the American Bankers Association, found consumers prevailed more than half the time.
Arbitration clauses can help companies avoid class-action suits like the one Nguyen tried to file against the cell phone company.
"It's just appalling, actually, that they can just change the terms and just say, 'Hey, these are the new terms and you're stuck with them," says Hoang.
Nguyen is now filing for arbitration.