(Adds guidance, results)
Oct 28 (Reuters) - T-Mobile US Inc on Monday beat analysts' third-quarter estimates for net new phone subscribers who pay a monthly bill, boosted by competitive wireless plans aimed at fending off its bigger rivals.
The third-largest U.S. wireless carrier by subscribers said it added 754,000 phone subscribers on a net basis in the three months ended Sept. 30, compared with 774,000 additions a year earlier.
Analysts had expected 742,600 new subscribers, according to research firm FactSet.
Investors pay close attention to postpaid customers, or those with a recurring bill, because they are more valuable to carriers and tend to remain with the company longer than prepaid users.
T-Mobile faces a state attorneys general lawsuit, led by New York and California, as it works to buy Sprint Corp and achieve more scale to compete with larger operators such as Verizon Communications Inc and AT&T Inc.
While T-Mobile and Sprint have been locked in a lengthy merger process, Verizon and AT&T beat Wall Street estimates for net new phone subscribers.
Bellevue, Washington-based T-Mobile said it expects pre-close merger-related costs to be $125 million to $150 million before taxes in the fourth quarter.
The company said it now expected adjusted core earning target for 2019 of $13.1 to $13.3 billion, up at the midpoint from prior guidance of $12.9 to $13.3 billion.
T-Mobile's third-quarter net income rose to $870 million, or $1.01 per share, from $795 million, or 93 cents per share, a year earlier. Analysts had expected earnings of $1.01 per share, according to IBES data from Refinitiv.
Revenue rose 2% to $11.06 billion, missing estimates of $11.33 billion.
(Reporting by Noor Zainab Hussain in Bengaluru; Editing by Maju Samuel and Sriraj Kalluvila)