Your iPad can’t make or receive calls or texts by itself, but there’s an easy workaround if you want to use your iPad for these things. You’ll just need to link your devices to allow these things to be routed through your iPhone.
First, ensure you’re logged into the same Apple ID on both devices.
To enable phone calls on an iPad: on your iPhone, open the Settings app and tap Phone > Calls on Other Devices. Turn the toggle on and then choose from the list which of your other Apple devices you’d like to allow calls on.
To enable SMS text messages on your iPad: on your iPhone, open the Settings app and tap Messages > Text Message Forwarding. You should see a list of your other Apple devices – simply toggle your iPad on from this list.
Note that even without linking up, an iPad can still send and receive iMessages and FaceTime calls as these can operate via a normal internet connection and don’t require a cell plan.
Using the same technique, you can also route calls and texts through to a Mac. Pretty handy!