What happens when I sell the phone? Can you take the tags off? Or am I obligated to use the service if someone sends it back (as the new owner)? Also what happe

What happens when I sell the phone? Can you take the tags off? Or am I obligated to use the service if someone sends it back (as the new owner)? Also what happens if in the time that I lost the item, I've replaced it. Then do you keep my phone? Sell it?