Probably (I've read that there will be a switch in the carrier settings for T-Mobile USA), but also why would you want to? In the end, the Starlink satellites

Probably (I've read that there will be a switch in the carrier settings for T-Mobile USA), but also why would you want to? In the end, the Starlink satellites will be just another set of cell towers, just with a slightly unusual velocity and altitude. You already can't e.g. disable using T-Mobile base stations leased by a particular land or infrastructure owner.