Apple Watch battery is dead. How to get it repaired?

I found my old iWatch in my packed stuff from when i moved overseas. The battery is dead, tried charging it for 2 days, as well as a hard reset. And still will not turn on. Is it possible to fix by bringing it in? And if so, i don't have any receipts, or proof other than it would show my account IF it comes back on.

[Re-Titled by Moderator]