ipad (cellular): how to receive/send texts

Hi,

I have an ipad (cellular), current iOS 11.3 here. How do I receive and send text messages on it?

A similar question has been asked here a lot, but with an important difference: I do NOT want to know how to forward a text that has been sent to an iphone further onto an ipad (iMessage).

I want to know how an ipad with a SIM card in can natively receive texts on that SIM. Without any iphone.

I mean, it's a GSM device, it's supposed to be able to do that, right?

If I open the "Messages" app, then I can actually write and send an SMS, but it never is received anywhere. Also I can send a text from another device to my SIM card, but it never arrives on the ipad.

That problem adressed, my next problem is: I want to forward that text message onwards to an iphone. So the exact opposite direction this is normally being used.

My scenario is: I have two SIM cards (work and private). But I don't want to carry two phones with me. So I have one SIM set to call forward and only carry one phone. In order to not miss out on texts, I want them to be forwarded. So I put the second card into the ipad and want the texts to be forwarded via iMessage to the iphone.

But on the ipad, in "settings -> messages -> send&receive" for some reason I will not have my SIM's number listed. It will just not appear, whatever I do. It shows the number of my iphone, obviously imported from the AppleID account, but that's not the point.

The ipad will not add the number of its SIM card to the AppleID/iMessage account.

I briefly managed to get both numbers connected to my AppleID/iMessage account by swapping the SIM cards. So the iphone got the other SIM in and added the number to the iMessage account, "messages -> send&receive" did show both numbers. But after swapping the SIMs back, it did disappear again after minutes.

So basically: I don't get it. How can I operate two numbers at the same time?

i mean, it's both iOS devices on the same OS version, how comes they act so differently?

Why is this not working?

Also the option "forward message" is missing in my ipad's "settings -> messages" dialog.

Can someone help, please? Thanks!