As many as one in four current iPhone users may switch off their AT&T service now that Verizon has confirmed it will offer Apple's iPhone, according to a survey published this week.

The ChangeWave Research survey of 4,000 AT&T customers found that 26% plan to switch to Verizon this year, and that the majority of those who intend to switch will do so within the first few months of 2011.

The results of the survey shouldn't be too surprising. Virtually ever since the product was first released in 2007, iPhone users have griped about AT&T's shoddy voice quality, dropped calls, and service interruptions, particularly in major metropolises like New York and San Francisco.

AT&T has said it's upgrading its infrastructure to improve service, but it may be too late. Many reports indicate that it was AT&T's poor performance that led Apple CEO Steve Jobs to end the carrier's exclusive rights to the iPhone and award additional rights to Verizon.

After months of speculation, Verizon Wireless formally announced its deal to carry the iPhone on Tuesday—and the company wasted no time taking an implied dig at AT&T.

"We are pleased to introduce millions of wireless uses to the industry leading iPhone 4 on the nation's most reliable network," said Verizon president and chief operating officer Lowell McAdam, in a statement. "This is an important step for the industry as two great companies join forces to give wireless customers one of the most important technological additions to the mobile landscape this century," said McAdam.

iPhone 4 officially goes on sale through Verizon starting on Feb. 10. Prices start at $199 for the 16GB model, with a two-year contract, and $299 for the 32GB model, with a two-year contract. The device will be sold at Verizon stores around the U.S., as well as at Apple Stores and through Apple's online shop.

Amazon officials confirmed this week that their site will not offer the Verizon version of iPhone 4.