Verizon Wireless made its most significant foray to date in the unlimited prepaid calling market, rolling out a new rate plan yesterday that provides unlimited voice, text and basic Internet access services for an upfront payment of $50 per month without a contract. Although Verizon has previously offered customers prepaid, à la carte options that provide, for example, voice service at $1.99 per day or unlimited text services at $20 per month, Verizon’s announcement represents the company’s first major effort to achieve a competitive foothold against popular prepaid offerings marketed by MetroPCS and Leap Wireless as well as Sprint’s Virgin Mobile and Boost brands. As a consequence of weak economic conditions that have induced some wireless customers to shy away from extended service contracts, the prepaid market is experiencing healthy growth. Statistics show that the prepaid segment of Sprint’s customer base grew by 23% by the end of June, while MetroPCS boosted its prepaid customer base by 19% during the same period. Initially, Verizon’s new prepaid plan will be limited to four lower-end “feature” phones, manufactured by LG Electronics, Samsung and Pantech Co., that lack the full web browsing capabilities of smart phones. Although Verizon expects to add more handsets to its prepaid lineup at a future date, new and existing contract customers with smart phones will not be eligible for the prepaid offering. (Earlier this year, Verizon eliminated unlimited data plans for smart phone contracts.) Current customers with older model feature phones, however, may sign up for prepaid service if their handsets are compatible with that service. Observing, “in these times, there are some people who would prefer living on a prepaid plan,” a Verizon spokeswoman explained, “this is a very competitive market, and we want to make sure we have a price portfolio to fit a greater number of customers.”