A week after Sprint kicked off its “Cut Your Bill in Half” promotion, T-Mobile US launched the  latest salvo in an apparent price war among the national wireless carriers by rolling out a new family plan on Wednesday that  offers unlimited LTE data access as well as unlimited voice and text service at a monthly rate of  $100 for two lines.

T-Mobile’s  latest  offer  comes  as  wireless  market  leaders  Verizon  and  AT&T  confirmed   that  they  would  scale  back operational forecasts for the fourth quarter.  Since embarking on its “uncarrier” marketing  campaign eighteen months ago in which it eliminated subscriber contracts and handset subsidies and introduced rate plans  undercutting those of its rivals, T-Mobile has experienced steady gains in subscribership that include the addition of 2.3  million new customers during the last quarter. At an investor conference this week, AT&T  acknowledged that the aggressive pricing moves of its rivals are resulting in subscriber churn that  is forcing the company to invest additional money in efforts to lure customers.

Sources say that the new monthly rate of $100 for unlimited voice, text and data is $40 lower than  T-Mobile’s comparable “Simple Choice” rate plan for two lines of service. For an additional monthly  charge of $40 per line, subscribers will be able to add up to ten additional lines to the $100  family plan.  T-Mobile also said it would re-introduce a four-line plan for $100 per month that provides each line with 2.5 GB of monthly data use, plus unlimited voice and  text service. The 2.5 GB allowance would extend through the end of 2015, after which the plan would revert to 1 GB of data  per line per month.

In remarks to reporters, Terry Hayes, T-Mobile’s regional vice president for the northeast region,  pledged that customers’ data usage would never be throttled.  Stressing that “customers are getting  these high-end smart phones and they want to use these phones,” Hayes proclaimed that “families won’t have to police data or worry about  overages.”