Verizon and AT&T don't have lease programs and, like T-Mobile, principally sell phones through zero-interest installment plans or for the full price at the time of the purchase.
Which leaves Sprint alone among the four national carriers.
"They are literally the only company in America that will charge you more for your phone than the phone costs itself," said Walter Piecyk, an investment analyst who follows Sprint for BTIG Research.
Sprint won't say how much out-of-term revenue it collects from customers. A spokesman said it affects "a very small amount of customers" relative to the company's 54 million subscriber base.
Leases, however, are how the Overland Park-based wireless carrier chooses to do business with high-value, creditworthy consumers.
Roughly 90 percent of the new customers who met a credit check to sign up with Sprint this summer signed leases. The others bought their phones upfront or already owned them. Sprint no longer offers an installment plan for buying a phone over time. Prepaid customers, who buy wireless service month-to-month, don't qualify for installments or leases.
A Sprint lease can work like an installment plan -- if the customer pays attention and plays by the ground rules.
Ignore the rules -- and the reminders Sprint says it sends to its lease customers repeatedly -- and you end up like Moody, paying more for a phone than it cost originally. Potentially a lot more.
The day before Moody's discovery, Sprint's CEO explained the company's out-of-term leasing practice during a session with investors and analysts. He was pointing out the benefits to Sprint.