I'm trying to get a 4G signal on a new Alfa line I bought just for mobile data.
I have a USIM, data plan is activated, 4G is selected in settings, APN is "alfa" - but no matter what I only get 3G.

Does anyone have any clue why this might be happening? Device is iPhone Xs Max.
Call Alfa, most probably it's a mis-configuration of your phone (happens all the time when you switch phones, the automatic settings for 3g/4g don't work), they will guide you through how to manually set it.
I called alfa, they “activated” 4G. I’m guessing they just gave me access to it or the likes since you can’t really activate such a thing. Thanks to those who answered!
I used to have an alfa data sim, i dont know why but they activate 4g after 24 hours of activating subscription or changing plans.
If this the case dont let the bundle subscription ends or you will have to wait 24 hours again once you resubscribed.