You can relay phone calls and text messages through your iPhone to your iPad, so it’s easy to stay in touch no matter what device you’re on.
Use your iPhone to make and receive phone calls or messages on your iPad.
Note: Cellular charges may apply. Wi-Fi Calling isn’t available from all carriers.
Make sure of the following:
Both devices have Get started with FaceTime on iPad.
If you’re using a VPN, make sure its configuration does not prevent local networking as that may interfere with some Continuity features.
Go to Settings What is the difference between iMessage, RCS, and SMS/MMS?
To send and receive iMessages on iPad, see Make a call with Wi-Fi Calling.