A fresh research report shows that the cell phone service from AT&T (NYSE: T) is getting worse despite the company's efforts to improve the network. But something smells fishy around these numbers.

According to market research firm ChangeWave, AT&T drops more calls than any other American network, leading to terrible customer satisfaction and a widespread desire to switch to some other provider. Verizon (NYSE: VZ) Wireless is the consistent leader across all of the elements examined, typically followed by Sprint Nextel (NYSE: S) and Deutsche Telekom's (NYSE: DT) T-Mobile arm, in that order.

ChangeWave posits the main thing that keeps AT&T hanging on to a 33% market share is the exclusive access to Apple (Nasdaq: AAPL) iPhones. "If Verizon were ever to offer the iPhone, the evidence points to it having a profound and likely transformational impact on the industry," says the research note. That may very well be true, but I flat-out don't believe some of the study's claims.

AT&T representatives were quick to point out counter-evidence of their own. Another recent study showed AT&T's voice network to be indistinguishable from Verizon's when it comes to dropped calls, backed by actual field tests across the country. The ChangeWave report is based on user surveys, which brings two big problems into the picture: for one, ChangeWave's sample is probably skewed, since survey responses were collected from the rather exclusive club of ChangeWave members. Second, and even worse, self-reporting introduces human error and plain forgetfulness. How many of your cell phone calls have dropped in the last three months? Yeah, take a guess. Many of ChangeWave's respondents probably did the same.

So in many ways, this study probably shows customer sentiment in a subset of high-end users, rather than actual call performance. Verizon's dominance here shows how good the company's "most reliable network" advertising is.

AT&T should worry about it, though. Methodology issues aside, there seems to be a great deal of vitriol in the air around AT&T these days. If and when Verizon gets its hands on the iPhone, there's a very real risk that plenty of iPhone customers will migrate to Big Red in a heartbeat.

That might not be such a bad thing for AT&T in the long run, but it'll hurt for a while.

Do you believe in ChangeWave's dyspeptic view of AT&T and its network? Share your thoughts in the comments below.