Today, T-Mobile's own Nevile Ray, Chief Technology Officer for the carrier, tweeted that the carrier has managed to deploy more 600 MHz spectrum across 257 new cities in the United States. T-Mobile has not stopped investing into its network and this 600 MHz band (also known as Band 71). T-Mobile paid a hefty lump of cash when the FCC was auctioning off unwanted TV broadcast spectrum (the spectrum whose purpose was for OTA analog TV signal). The other carriers didn't bat an eye at the opportunity to purchase more spectrum but T-Mobile went all-in and is still deploying this low-band...
Source: https://www.gsmarena.com/tmobile_deployed_600_mhz_band_in_257_new_cities_over_the_last_couple_of_months-news-34046.php