>> Does that mean that you can only order for a cab via an app? Or are apps an alternative?

Well, apps are my primary way of ordering cabs now, because I can set the pick-up and drop-off precisely by map, and track the vehicle before it arrives etc.

But they still have their phone lines too.

I'm not an original OP, but in my city there's a centralized call center and several apps -- you may choose to use whichever you prefer as most cab companies support all or at least many of them.