• by Mark Walsh  @markfwal, September 10, 2009

It looks like the battle over calling plans is heating up again. A day after AT&T introduced a service offering unlimited mobile calling to five people on their "A-List"-similar to T-Mobiles MyFaves and Verizon Wireless' Friends and Family options-Sprint has upped the ante.

The carrier's new "Any Mobile Anytime" feature for its $69.99 "Everything Data" plan offers unlimited calling to any U.S.-based mobile phone along with unlimited messaging and data services including SMS, MMS, Sprint TV, GPS navigation and more. The Everything Data plan includes only 450 minutes of landline calling. But who uses up all their monthly voice minutes, anyway?

"T-Mobile MyFaves, Verizon Friends and Family, and AT&T A-List be damned-Sprint's 'Any Mobile, Anytime' is now the affordable plan to beat," stated Boy Genius Report in a post today.

Sprint also takes direct aim at AT&T's and Verizon's already shrinking wireline businesses, telling consumers its new unlimited mobile-to-mobile calling offer "makes it easy for individuals and families to cut the cord and save money." Sprint even enlisted the help of influential wireless analyst Roger Entner of Nielsen to tout the plan.

"The new Any Mobile, Anytime feature should be attractive to the middle market of customers, especially families with multiple lines," said Entner in a statement in the Sprint announcement. "These are people who are likely to be cutting the cord and regularly calling other cord cutters." (Nearly a quarter of U.S. households have gone mobile-only, according to wireless research firm Chetan Sharma.)

Unlike AT&T and Verizon, however, Sprint has continued to lose postpaid, or contract, wireless customers, to the tune of nearly 1 million in the second quarter. Only the 938,000 prepaid customers added by its Boost Mobile arm helped offset overall wireless customer losses. Boost's $50 monthly unlimited voice and data plan launched in January has helped attract new customers.

Still, the other major carriers may now feel they need to tweak their own calling plans to match or one-up Sprint's latest move. As one commenter on Boy Genius Report noted: "This puts pressure on the big 2 (AT&T and Verizon) to adjust prices, attracts users looking for a better rate for a common phone, and squeezes the Boosts and MetroPCS price points while adding full data and a thick roster of smartphone offerings."

And with Sprint adding the Palm Pixi Wednesday, and the new HTC Hero device from Motorola next month, to its roster of smartphones, the carrier is aiming to challenge its larger rivals on that front as well.