Use FaceTime with your iPhone nearby and signed in to the same Apple ID
On iPhone, go to Settings > Phone > Calls on Other Devices and turn it on
On iPad, go to Settings > FaceTime and sign in with the same Apple ID
On iPad, open FaceTime
Tap the plus button or search for a contact
Enter a phone number or choose a contact
Tap the audio call button
Use a third-party calling app such as WhatsApp, Skype, or Zoom
Open the app on your iPad
Sign in to your account
Select a contact or enter a number
Tap the call button
Use Wi-Fi Calling through your carrier if supported
Set up Wi-Fi Calling on your iPhone and carrier account
Make the call from your iPhone and continue it on your iPad through FaceTime audio if enabled