Taxi service may be a lot different from what you have in your country. Here in Italy, Taxi service is a public service and therefore heavily regulated.
Let’s start whith one big diffence: don’t look for different cabs companies. There are none: all Taxis are white, with sign on top. And that’s it. All same fares, all same meters.
You may notice there are some different stickers, with different phone numbers: that’s just different ways to get in touch with a car.
If you need a Taxi, you may call 02.7777 or use the official app for Android here and iPhone here. Double check they do accept cards if you don’t have cash, but vast majority do.
Remember: meter starts when the car is engaged, so you most likely will find some charges already on the meter when it reaches your address.
Even if “illegal taxis” are extremely rare in Milan, always use regular white taxis, with taxi sign on top and with working meter. This will guarantee you a professional driver with a professional driving licence (including frequent drugs\skills tests).
This is how they ALL look like:
Remember: all you have to pay is what’s shown on the meter. Nothing more.
If you want to use UBER or similar services, have a look here.