How do I buy music on my iPhone 7?

So I want to buy music for my iPhone 7. I've been looking all over my phone and I have no clue how to do it. I've looked on the music app, and it says you have to pay monthly. What happened to just buying music and keeping it on your phone? Can I still do that? Or does it have to be done like this now?

The iTunes app. That's where you buy the track(s) you want & call it a day vs what is in the Music app (Apple Music) where you pay to stream music monthly.