Small and midsize business customers who use Verizon will now have the option to get unlimited wireless calling between a Verizon phone number and up to five wireline numbers, the company said Wednesday.

Enterprise customers will pay $4.99 per wireless line, and calls to five business wireline numbers will not be charged against the business customer's wireless minutes. Those already subscribed to Verizon's Freedom for Business plan are eligible for this calling option.

"Every penny counts for small businesses, and Verizon Freedom for Business with Wireless Voice allows small-business professionals to make unlimited calls to the business numbers they call most without using wireless minutes," said David Frendo, director of small-business products for Verizon, in a written statement. "Taking advantage of this total calling solution helps our customers save money and increase productivity, no matter where their daily business takes them."

This latest move shows the increasing competition between Verizon and AT&T. Earlier this year, Verizon unveiled a $99-a-month unlimited calling plan, AT&T and other carriers quickly followed suit.

While the consumer market is vital to each company, the enterprise market is a key source of growth. Beyond voice, providing mobile workers access to data can generate a lot of revenue for carriers, as the monthly access fee averages $60 per user.

Currently, AT&T is the largest wireless carrier, with 71.4 million subscribers. But, if Verizon's acquisition of Alltel goes through, Verizon's reach will extend to about 80 million subscribers.