Can't add new phone number to Sim on OnePlus Nord 2 5g

I recently moved over to the above phone. When I try to add a new phone number to my contact list I only get 2 options.

Add to:
*_____@gmail.com or add to:

*Phone/device

But no 3rd option to add to Sim card which I've had on previous phones.

Any ideas how I can do this, thanks.