Cable giant Comcast will start selling cellphone plans called Xfinity Mobile in the coming months, using a network it's leasing from Verizon.

Unlimited data, talk and text will be available by mid-year for $65 per line for up to five lines, or $45 per line for customers with Comcast's top X1 packages, which bundle together TV, internet and phone services. Alternatively, customers can opt to pay $12 per gigabyte each month.

Xfinity Mobile will launch on Verizon's airwaves as part of a 2011 agreement between the two companies. It will employ Comcast's 16 million Wi-Fi hotspots within its footprint, allowing customers to automatically switch onto Wi-Fi from 4G LTE.

"We're doing mobile differently by bringing our customers the best networks and a product designed to save them money in an increasingly data-driven world," said Greg Butz, president of Comcast Mobile. "Mobility is more important than ever to consumers, so we've designed Xfinity Mobile the way mobile should be - a simple solution for internet and entertainment in and out of the home."

In recent months, the four major U.S. wireless carriers - Verizon Communications, AT&T, T-Mobile US and Sprint - have offered unlimited data plans ranging from $50 a month for a single line to $90 a month.

Comcast rival cable provider Charter Communications is also planning to launch a wireless service in 2018.

Comcast will limit the service's rollout to customers within its footprint, which includes major markets like Philadelphia and Chicago. It will initially be available only to subscribers who have Xfinity broadband service.

The wireless service will be available on Apple's iPhones as well as the Samsung Galaxy phones.

The service Comcast is selling will be essentially the same as a Verizon plan, though Comcast will reduce speeds on unlimited plans after 20 gigabytes.

Comcast's pay-per-gigabyte approach is similar to what Google is doing with its wireless service, Google Fi. Both plans charge them only for what they use.