So I've had my Switch for a while now, and never thought more about the account that the seller I bought it from had linked to the Switch. Now, it has been a year since I bought the Switch, and it is getting annoying having to select my user when starting a game each time. I do have a full NAND backup before I touched it on Firmware 2.3, but I have no idea if that is gonna help me in this. Is there some way to unlink the account?