Updated: Sprint kills unlimited data for life guarantee for customers who choose new unlimited or family plans

Sprint (NYSE: S) is discontinuing its offer of guaranteed unlimited voice, texting and data for the life of the phone line for new customers who choose its recently introduced individual and family data plans. However, it will still be available to new customers who choose its older Unlimited, My Way and My All-in plans. The carrier disclosed the change in conjunction with its announcement of a new unlimited talk, text and data plan for individuals that costs $60 per month.

Sprint instituted the guarantee in July 2013 shortly after SoftBank finalized its deal to buy 80 percent of Sprint. The Unlimited Guarantee was given to new customers who signed up for service as well as existing customers who switched to Sprint's Unlimited, My Way or My All-in plans.

Unlimited, My Way plans offered unlimited voice, texting and data on the Sprint network for $80 per month, and the My All-in plan offered unlimited voice, texting and data plus 5 GB of mobile hotspot usage for $110. Both of those plans came with the Unlimited Guarantee--but the new $60 unlimited plan does not.

Sprint spokeswoman Adrienne Norton told FierceWireless Guarantee is still available to new customers on Unlimited, My Way and My All-in plans, but not to customers who choose the $60 plan or Sprint's Family Share Pack plans. Existing customers who have that benefit on their account will retain it as long as eligibility requirements are met, she said.

Norton said customers who signed up with the Unlimited Guarantee will still have access to unlimited voice, texting and data while on the Sprint network--as long as they stay on a rate plan that includes the Unlimited Guarantee and the account remains in good standing. 

The Unlimited Guarantee fit with Sprint's longtime mantra of offering unlimited service to customers and was a way to reward loyalty and decrease churn. The fact that new customers can no longer get the guarantee and existing customers will not be able to get the new, lower pricing if they want to keep the lifetime guarantee could undercut Sprint's efforts to attract and retain subscribers.

Sprint's new $60 plan undercuts T-Mobile US' (NYSE:TMUS) $80 unlimited data plan by $20 and is available to existing Sprint customers as well as new customers. Sprint's $60 price does not include the cost of a phone; customers can either purchase a new phone through Sprint's Easy Pay handset upgrade program and pay for it in monthly installments, or they can bring their own phone, or they can purchase their phone at full price.

Earlier this week Sprint announced new shared data plans for families that essentially offer double the data that Sprint's rivals offer. David Owens, Owens, Sprint's senior vice president of product development, told FierceWireless the carrier did so because it thinks its network can support large amounts of data usage and wants to provide value to customers. However, the removal of the unlimited for life guarantee for some new customers seems to undercut that.

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Correction, Aug. 23, 2014: This article incorrectly stated which plans are no longer eligible to receive the Unlimited Guarantee. It will still be available to new customers who choose its older Unlimited, My Way and My All-in plans, but not to new customers who sign up for Sprint's recently introduced individual and family data plans.