Ipad cellular feature

An iPad, whether a Cellular model or not, is not capable of accessing Cellular Voice or Messaging features. An iPad with Cellular connectivity alone can only access IP-data services.

If paired with an iPhone, the capabilities of iPad significantly broaden to include Cellular Voice and Messaging services of the iPhone - relayed to the iPad over WiFi using Apple’s continuity features.

Continuity

https://support.apple.com/en-gb/HT204681

SMS/MMS Messaging

https://support.apple.com/en-us/HT208386

WiFi Calling

https://support.apple.com/en-gb/HT203032

When correctly configured, the iPad FaceTime App provides access to Cellular Voice Calling features - whilst Messages supports SMS/MMS messaging services.

No, the iPad only support cellular data.

But to some degree you can enable calling on it:

Allow phone calls on your iPad, iPod touch, and Mac - Apple Support

If your carrier supports WIFI calling:

Make a call with Wi-Fi Calling - Apple Support

You can also make and receive calls with Facetime and facetime audio:

Use FaceTime with your iPhone, iPad, or iPod touch - Apple Support

Good luck!