Boost Mobile kicks off a promotion deal for new customers, slashing the unlimited 4G LTE prepaid plan from $55 a month to $35 a month for customers signing up before March 31.

Boost Mobile, the prepaid mobile carrier in the U.S., is bringing an attractive promotional deal for new customers that slashes the monthly unlimited 4G LTE plan by $20 a month for first six months, starting Thursday. The new $35 a month plan includes unlimited talk, text and data for customers signing up with the network before March 31, 2014.

Boost Mobile's offer for new customers not only saves $120 over the course of first six months, but also cuts the original price of the plan by $5. So, customers will end up paying $50 a month for unlimited talk, text and data instead of $55. The high speed LTE speeds will stall after 2.5GB, and video is limited to 3G speeds.

New customers will also qualify for Shrinking Payments, where the monthly bill drops by $5 after every six on-time payments. With Shrinking Payments, a user's monthly bill goes as low as $40 a month. With no contracts necessary, customers can purchase an eligible Boost 4G LTE smartphone and sign up for the offer directly through the carrier, Best Buy, Radio Shack and other Boost-affiliated retailers.

The carrier offers a handful of 4G LTE devices like iPhone5S, iPhone 5C, Samsung Galaxy SIII, Boost Warp 4G, HTC One SV, Boost Force and LG Optimus F7. Also, the carrier relies on its parent Sprint's network for 4G LTE coverage, which is currently expanding and is available in 340 markets across the U.S. and Puerto Rico.

It is a tad hard to compare the less-dominant prepaid plans with service contract plans, which usually bring the ease of paying the total cost of the phone in monthly installments. T-Mobile simplified the process of buying a new phone and pay in installments without the need to sign up for a contract. This triggered other carriers to adopt the new methodology to maintain their dominance in the highly-competitive market.

Comparing Boost Mobile's new offer with Target's prepaid plan, which was announced October last year, the Sprint-owned Boost prepaid plan steals the edge. Target's prepaid plan, powered by T-Mobile's network, offers unlimited talk and text but no data for $35 a month, and unlimited talk, text and data with initial 1GB at 4G LTE speeds for $50. For the unlimited data with 4GB 4G LTE speed, customers must be willing to pay $65 a month.