I have a new Samsung Watch 6 LTE and need help using it without the phone

The watch has another (its own) line (another phone number) though it is linked to my phone number that I had already before purchasing the watch. Obviously you don’t want to suddenly have one more number to use, but the number assigned to the watch is not meant and cannot be directly used, for example cannot call that number. I was told that each device must have its own number, kind of place-holder in T-Mobile’s system. Silly solution IMHO. Still, as said, I cannot text or call from the watch if the phone is turned off. @gramps28 how exactly do you set this up, what are the steps, where in the settings is that option? And I still wonder why this needs to be set up and not happens by default? Is there anybody who wants the watch not usable when the phone if turned off?