Xm5's headphones right ear not working

It was fine 5 days ago. I was watching a YouTube video and then the volume slowly shifted over to the left side of my headphones and now I'm stuck with a pair of headphones that only work in ONE side. For $400 that I bought initially when the hype was huge around these headphones, they seemed good in practice, but now I'm at a loss and I don't know what to do. Before that I also had some wierd cackling noises coming from the left ear cuff and HEAPS of other problems like the volume control would change itself too and double click randomly. Man I feel so ripped off, and I bought this pair like 7 months ago brand new on ebay from a legitimate seller. Please if you're on the fence on buying these headphones, just don't. I actually don't know what to do, any help?