Cellular Service on New iPad Pro

You can place VoIP calls such as Facetime, or Skype, but you cannot place cellular calls like you would with your phone to other cellular devices.

The Cellular hardware only allows data usage for internet access.

If connected to an iPhone using Continuity it can then place calls through the iPhone to other cellular devices when both it and the iPhone are on the same Wifi network.

See here: Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch - Apple Support

In addition to allowing access to network, via cellular services when you’re not connected to a WiFi network - there is one other major consideration...

WiFi ONLY iPads do not have any GPS capabilities - whilst WiFi & Cellular models do have full GPS/aGPS capability.

As such, if location-based services are likely to be important to you, then you should definitely consider an iPad with Cellular capability - even if you do not intend to purchase an air-time contract from a Cellular provider.

Hope this is some help to you.

LP

The cellular option allows the iPad to connect to a cellular network and get internet access (data) when there is no Wifi available.