You can make and receive calls on your ipad by using wi-fi calling to relay calls through your iphone required ios 9 or later. Cellular charges may apply. Wi-fi calls are not available by all carriers. If you’re not sure which carrier you’re using, check with your service provider. Voice over Wi-Fi (VoWiFi)
If you’re using a Wi-Fi network, you can make and receive calls over that network by using Voice over Wi-Fi (VoWiFi). This lets you talk for free over your Wi-Fi network on your iPhone, iPad, Apple Watch, and Mac. Voice over Wi-Fi works best on Wi-Fi networks with a strong connection.
You can also make and receive phone calls over your home Wi-Fi network with the following supported devices:
iPhone
iPad
iPod touch
Mac