At the upper end, the AT&T FamilyTalk Nation 2100 plan costs $109.99 a month for 2100 minutes calling to or from a landline phone, making the total $139.99 with the unlimited messaging required.

Phillip Redman, an analyst at Gartner who follows carrier billing, said the new AT&T plan is another recognition by the carriers that voice traffic is diminishing while data traffic is increasing.

As a result, the revenue from voice traffic becomes less important to carriers, who still must find a way to convert users to data and messaging plans. "This seems like a great plan to move people onto text plans and increase that revenue," he said. "Too bad there isn't an offer for business users."

Jack Gold, an analyst at J. Gold Associates noted that the new AT&T plan "certainly isn't something for nothing."

"Yes, there are strings attached," he said. Gold agrees that tying the free mobile calls to texting is a way to find revenues from the trend toward increased text messaging.