"Go ahead and dial up those digits--no matter which wireless network youre calling," said AT&T in a press release Wednesday announcing the deal.
Customers will need a qualifying voice plan with unlimited messaging in order to subscribe to the feature, which will go live Thursday. Unlimited messaging costs $20 a month for individual plans and $30 a month for FamilyTalk plans.
Mobile to Any Mobile is an exciting offer that will keep our customers connected to the people they want to talk to, when they want to talk to them, without the hassle of watching minutes, said AT&T chief marketing officer David Christopher, adding that the carrier "offers the most flexibility in the industry.
The timing, of course, is meant to steal the show from Verizon Wireless. After years of waiting, Verizon will release the CDMA iPhone 4 Thursday at 7 a.m, though some customers report already having received and activated the smartphone.
Initial reviews of the Verizon iPhone 4 found essentially the same phone as the GSM iPhone 4, but with significantly less dropped calls.
AppleInsider reported last week that Verizon and Apple may have prepared as many as 2 million iPhone 4 units for the launch. Analyst Mike Abramsky with RBC Capital Markets believes sales of the handset will top 1 million in the first week.
According to Verizon, preorders of the iPhone 4 surpassed any first day launch in the carrier's history in just the first 2 hours of availability.
Demand for the smartphone has been "unprecedented," as shipping times for the device have already slipped to Feb. 18.
One recent survey found that 26 percent of AT&T customers plan to switch to the Verizon iPhone 4 and more than half of Verizon's existing Android and Blackberry customers are likely to switch to the iPhone. A January survey by ChangeWave discovered that 16 percent of AT&T customers would switch to Verizon if it began carrying the iPhone.