T-Mobile has confirmed the Oreo update for a couple of affordable Samsung devices on its network. The devices in question are the Galaxy J7 Prime and the Galaxy Tab E 8.0, with the carrier's website saying T-Mobile and Samsung have agreed to support Android version 8.0 for these handsets. Sadly, there's no information on when the update would start rolling out, and we are not expecting it to happen any sooner as Samsung is currently focusing on rolling out Oreo for its top of the line phones like Galaxy S8 and Note8. Source 1 2
Source: https://www.gsmarena.com/tmobile_confirms_oreo_for_samsung_galaxy_j7_prime_and_galaxy_tab_e-news-29143.php