Just got my tab s8 plus 5g, and I love it. some of you here might knew this already but if you don't then continue reading this, LOL, I been using my tab as a phone I do sometimes forgot to bring phone with me or was on charge at home.
To use your tablet as a phone you need a network sim and to log in with your samsung account same as the one you have on your phone, also do both setting on phone and tablet make sure sure you turn on call and text on other device.
to use your tablet as a phone without your phone near by or miles away from it, with the same mobile number that you got on your mobile phone witch you have with the network provider you with, all you have to do is on your phone and tablet go into call and text on other device setting make sure you disable WIFI, only make sure the toggle turn grey and you all set to go using tab without your phone nearby.
when you make a call to someone there will be a pop up bubble asking you what device you want to use, click on the name of you mobile phone not you tab, if you click on your tablet instead of your phone it won't send a call as your network sim for tablet is only data and text.