Calling from one iPad to another with same phone number
My granddaughter is using my old iPad with the same phone number as mine. How can we call each other on FaceTime?
iPad Air, iPadOS 17
Are both devices signed-in to iCloud with the same AppleID? If so, you'll not be able to use FaceTime to call between devices. This limitation aside, sharing the same AppleID between users is a very bad idea - as sensitive information can be unintentionally accessed/changed and/or you can become locked-out of your AppleID account.
As for the phone-number - an iPad, whether a Cellular model or not, is not capable of directly accessing Cellular Voice or SMS/MMS Messaging features. An iPad with either WiFi or Cellular connectivity alone can only access IP-data services.
If you have added a DataSIM and Cellular plan to a WiFi+Cellular model of iPad, the number associated with the SIM card is only used to identify your account for billing purposes. This number is not used for making calls or sending messages.