Verizon Wireless plans to introduce a less expensive–but restricted–data plan for smartphone customers next week, according to a person familiar with the plans, in a move that follows AT&T Inc.’s own offer of two tiers of pricing.

The nation’s largest wireless carrier by subscribers will offer a $15 monthly plan that gives customers 150 megabytes of data starting Oct. 28. But unlike AT&T, it will keep available its $29.99 monthly unlimited data plan. The change was first reported by technology news Web site Engadget.

The move is part of a broader shift by carriers to change how they charge customers for the use of Internet, email and music downloads through their cellphones. Carriers have to juggle offering these data services at a fixed rate with sufficient investment in the underlying networks to ensure the traffic flows smoothly.

But the lower-priced data plan has also proven to be a boon for AT&T, luring new customers into upgrading to a smartphone. Verizon Wireless hopes the introduction of its $15 plan–which for now is considered a holiday promotion for the fourth quarter–will pay off in the same way.

“It’s designed to make data more affordable for entry-level users,” said Roger Entner, an analyst at Nielsen. “There’s a large number of people who simply can’t afford $30 for data.”

The $15 monthly charge would last throughout the life of the two-year contract.

Verizon Wireless will look at how successful the plan is before deciding whether it will extend the offer permanently, the person said. The new option is seen as a more affordable plan that can better compete with AT&T’s own tiered offering.

Verizon Wireless–which is jointly owned by Verizon Communications Inc. (VZ) and Vodafone Group PLC (VOD, VOD.LN)–could also make significant changes to the plan next year once it begins offering its fourth-generation wireless services. It is scheduled to launch its 4G network in 38 markets by the end of this year, and is expected to offer different plans for the service.

The carrier has also left the door open to a move away from unlimited data plans ahead of getting the Apple Inc. (AAPL) iPhone. Verizon Wireless will sell the device early next year, The Wall Street Journal earlier reported.

Carriers have been wrestling with how to introduce limits to stave off the exponential growth in data usage. Sprint Nextel Corp. (S) has kept to its unlimited offering, but charges $10 extra a month for phones with heavy data usage. T-Mobile USA, a unit of Deutsche Telekom AG (DTEGY, DTE.XE ), has spoken about throttling, or slowing down the connection for heavy users.

Verizon Chief Executive Ivan Seidenberg said last month he expected to offer a tiered model over the next four to six months.

Entner said he expects all carriers to eventually offer a lower priced, but restricted, data plan.

The new plan marks the first steps for Verizon Wireless. Customers who exceed 150 megabytes–which accounts to roughly 900 webpages or 5 hours of streaming music a month–will be charged 10 cents per megabyte. Existing customers have the option of moving to the less expensive option, or keeping their current plan.

In June, AT&T introduced its own restricted plans for data. Instead of a $30 unlimited plan, it began selling a $15 plan for 200 megabytes of data and a $25 plan for two gigabytes of data. Customers who went over their limit had to pay a charge of $15 or $10, respectively. Existing AT&T customers were allowed to keep their unlimited plans or switch to the less expensive capped plan.

Ralph de la Vega, head of AT&T’s wireless and consumer business, said in a recent interview that the lower-tier plan has been successful in signing up new customers. AT&T is slated to report third-quarter earnings on Thursday, with Wall Street expecting blow-out subscriber growth figures.

Verizon reports its quarterly results on Friday.

The new offer comes out the same day that Verizon Wireless will begin selling the Apple iPad, although the carrier is only selling the WiFi version.