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T-Mobile is offering free line with for customers on its One base unlimited plan, it said Thursday.

A study by Strategy Analytics showed its customers could use its free offers -- which include free Netflix, an annual Pandora subscription and discounted Live Nation tickets -- to save up to $1,550 per line each year, or up to $5,150 for a family of four.

"That's a significant benefit that no other carrier comes close to providing in comparable plans," wrote Susan Welsh de Grimaldo of Strategy Analytics.

The carrier celebrated by offering a free additional One line -- via monthly bill credits -- to customers who have a voice line and add one, for a limited time.

When asked to comment, T-Mobile didn't offer any further details on how long the offer will run.

It added 1.6 million net total customers this quarter, it noted on Tuesday, as it waits on regulatory approval to acquire Sprint.