Is it possible to change my premium site with another one using the same domain name? Many Thanks!
Yes, you can do that.
I haven’t done it often enough to give you instructions, but I think you’ll find what you need in the help articles below. One tells you how to reassign a premium plan, and the other shows you how to reassign a domain. My recollection is a bit fuzzy, but I think when you reassign the plan, there may be a step that offers to reassign the domain as well.: