How to file a claim for defective apple watch charger

less than a month after receiving my apple watch Ultra, it stopped charging. I was so convinced that the issue could not possibly be the cord that I filed a claim and sent the watch back for repair. I received the watch back and still would not charge. I then put it on my wife's old apple watch charger and it started charging immediately. Therefore, I have concluded that it is the cord that is not working, not the watch. I can't seem to find any way on the website to file a claim for the charging cord.