It's been a bit over two years since T-Mobile merged with Sprint. T-Mobile discontinued the Sprint brand four months later, in August 2020, but many legacy Sprint subscribers have still yet to swap ...
You can just buy a bare sim card at the T-Mobile store or online as well, I think it's $8 or something like that (with $5 of airtime credit). You can't technically activate the $30/mo plan in-store ...