> iPad with cellular does not really show you SMS's that's not from the carrier of the sim card.
Does iPad support SMS? The cellular line is usually only for data, https://www.howtogeek.com/710767/how-to-send-sms-text-messag...
iPads can't send SMS text messages through Apple's Messages app. Even if you have an iPad with a cellular data plan for mobile internet on the go, you still can't send SMS text messages.