Cellular Service

All models of iPad are available in two fundamental versions - these being WiFi Only and WiFi+Cellular models. Beyond these, models are differentiated by internal storage.

Note that whichever model you choose has internal hardware that cannot be modified or upgraded - and is fixed for the life of the device.

If its a cellular model, yes.

If its a Wi-Fi only model, then no.

You can't make a phone with an iPad, however.