I got the tmobile all in plan. The modeem doesnt come with external antenna ports?

So I’m testing out T-Mobile’s All-In plan. I thought the modem included supported external antennas? I got it, and it has 4–5 bars, but in the app’s metrics only one of the categories shows "Good." My tower is about 0.8 miles away, and that’s the one it’s connecting to. Im sure theres cheap antennas out there that would connect to it to help a lot. I just picked the all in plan because its extrenal mesh and thought this would support and antenna