Fail to receive verification code to my cellular iPad.

why i cannot receive my Messages on my iPad.

My iPad is cellular and a verification code do not reach my iPad notification whenever i want to access other application. PLUS, i dont have any other Apple device beside my Only iPad. I Also tried to go to iMessage —>receive message—-> and i do not know how to add my number phone to It. So i tried to go to my name and add no.tel at the contact but it need verification code. But my iPad cannot receive any message or call. Is there any solution to this? Oh, the data connection is still functioning only the message and call does not function.