T-Mobile (NYSE:TMUS) is once again taking aim at Sprint's (NYSE: S) customers, and this time it's using MetroPCS to do it.

T-Mobile's prepaid wireless business launched a promotion offering 22 percent to 50 percent off Sprint's Family Share Pack pricing to users of Sprint, Virgin Mobile or Boost who port their numbers to MetroPCS. Savings vary by the number of lines switched and by location due to differences in local taxes and fees.

Consumers who switch may also get a free MetroPCS LTE smartphone valued up to $50, or take a $50 rebate on any of the company's other phones. Users who add more than two lines will receive mail-in rebates rather than instant rebates.

The promotion marks the continuation of a frenzied holiday season that saw U.S. carriers aggressively pursue customers of rival network operators. Verizon (NYSE: VZ), AT&T (NYSE: T), T-Mobile and Sprint all launched substantial discounts during the holidays, and T-Mobile has been particularly active in pursuing customers of Sprint, which continues to struggle. On Black Friday, T-Mobile began offering $200 to Sprint users who switch in addition to a promotion to pay off early termination fees. Verizon, meantime, launched an ETF payoff promotion shortly after the holidays.

MetroPCS' offer also appears to be a response to Sprint's move in November to cut rates in half for customers who switch from Verizon, AT&T or T-Mobile.

Indeed, MetroPCS President Tom Keys subtly alluded to recent Sprint promotions: "For anyone who's been stuck or is regretting a recent switch to Sprint, this is a lifeline," Keys said in a prepared statement. "You can now get a bigger and faster network -- based on hundreds of thousands of crowdsourced tests -- for up to half the cost."

For more:

- see this MetroPCS announcement

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