Going by the findings of a March survey by ChangeWave, the Apple iPhone’s exclusive carrier, AT&T, has the highest rate of dropped calls amongst the leading US carriers – a fact that further accentuates the carrier’s problematic network.

The ChangeWave survey questioned 4,040 smartphone users about the percentage of dropped calls that they faced, on an average.

As per the statistics revealed by the survey, AT&T had a dropped call rate of 4.5 percent, which is notably higher than T-Mobile’s 2.8 percent dropped call rate; and Sprint and Verizon’s 2.4 percent and 1.5 percent respectively.

Comparing the March dropped-call statistics with the data collected in September 2008, it was found that while AT&T’s dropped call rate that time round was 3.6 percent, Verizon’s was 2.7 percent; thereby indicating that the situation has worsened for the AT&T network, though Verizon’s network has shown an improvement.

Commenting on the ChangeWave statistics, a not-too-pleased AT&T said that a “statistically valid drive test shows the AT&T network continues to deliver the nation's fastest 3G network and near best-in-class call retainability nationwide.”

The carrier further added that on a countrywide basis the calls dropped by its network accounted for barely 1.44 percent of all dropped calls, which it said is “within two-tenths of 1 percent of the industry leader and a difference of just two calls in a thousand - a virtual dead-heat.”