SIM vs Active

I went from another mobile provider to T-Mobile.  While my phone was ported successfully, at a retail store, my tablet wasn’t.  So I was being charged from the former company *and* T-Mobile for cellular data.  I had the other company disconnect the tablet and apparently it was done.  But under the Cellular settings, there are two statuses:  T-Mobile →  SIM (there is a checkmark next to it), Other provider → Active.  What is going on?