Sprint Nextel ( S) may be seeing customer attrition bottom out, according to rumors that rivals AT&T ( T) and Verizon ( VZ) are seeing fewer subscribers swap over from the struggling wireless provider.

Rumors have surfaced that the investor relations departments for both Verizon and AT&T were telling individual shareholders that fewer telephone numbers were being ported over from Sprint's wireless network. That speculation offers an explanation as to why Sprint shares have jumped 15% during the same week that the Dow Jones Industrial Average dropped 4% to its lowest level in 2008.

AT&T spokesman Michael Coe said the company was offering no comment on the speculation. Verizon spokesman Jim Gerace took a harder stance, saying that "Sprint continues to be our largest source of port-ins."

Gerace did acknowledge that Verizon's investor relations department has received several questions on the subject of ported numbers from Sprint, but he added that the company does not provide raw porting figures.

Sprint spokesperson James Fisher said the company would not comment on the rumor, adding that the second quarter is ending next week and that the company would not have any wireless churn data until its next earnings release in August.

"The fact that AT&T and Verizon are seeing fewer ports should not be too surprising," says Steve Clement, analyst with Pacific Crest Securities. "We're expecting churn to improve quarter-over-quarter for Sprint. However, there's no way of knowing how significant that is yet, and whether or not it justifies the price move in the stock."

Speculation heated up Wednesday after a JPMorgan Chase analyst released a research note quoting a Verizon executive on Sprint's recent success. Analyst Mike McCormack wrote that during a sit-down interview, Verizon President and COO Denny Strigl said that Verizon is "fortunate Sprint has stumbled, though Sprint has been doing better in last 30 days."

Strigl added that it was more important for Verizon to look at revenue growth than customer growth, which many took as a slight nod that the number of subscribers swapping over was indeed shrinking.

"To state the obvious, churn rates are only half the equation," warns Sanford Bernstein analyst Craig Moffett. "Keeping the customers you have is a pretty good start. There's also the related problem of getting new customers in the door. Anecdotally, gross additions have relatively been weak."

Moffett says that part of Sprint's rumored turnaround can be partly attributed to Samsung's new Instinct smartphone. Earlier this week, Sprint announced that the Instinct had become the fastest-selling EVDO handset in the company's history and that record sales have led to temporary shortages of the Instinct at some locations across the U.S.

The touch-screen device is priced at $129.99 (after a mail-in rebate) in order to better compete with Apple's ( AAPL) iPhone 3G, which is priced at $199 for an 8-gigabyte version that goes on sale July 11.

Moffett says that offering newer, more-attractive handsets such as the Instinct "is a huge step" but that one has to question the significance of Instinct's so-called "record-breaking" sales. Doubt over the announcement came after a Sprint spokesperson declined to release specific sales numbers and would not divulge which device previously held the sales record.

"Sprint hasn't had a big EVDO phone to compare this to," says Moffett. "They've sold out of the handset in lots of stores, which is clearly good news, but it's far from being definitive. It remains to be seen if sales are sustainable with both AT&T and Verizon reloading with the iPhone and Research In Motion's ( RIMM) Blackberry Bold.

Moffett says that if Sprint was indeed seeing churn rates decline, the company's next move should be to solve the problem it has articulating its value proposition to customers. Verizon has used the "Can you hear me now?" tagline for strategic positioning, and AT&T has the ubiquitous position with "More bars in more places," but Sprint has been unable to offer a "best network" strategy.

"Sprint is trying to carve out a more ambiguous position with the 'Now' network strategy," Moffett says. "The value proposition isn't quite as obvious. Why should someone pick Sprint when it's not quite as clear?"