When using iPhone 6s Plus with Bluetooth or wired headphones only one ear works?

I have an iPhone 6s Plus running the newest iOS that I have just bought this month. I noticed that wired stereo headphones only play out of one ear. So I took it to the Apple Store and had them take a look at it. They "fixed" the issue by giving me a new phone (same model, 64 GB). Same problem. I thought alright, I can't use wired headphones until Apple issues some kind of recall, I'll just get Bluetooth headphones and that should fix it. It's probably a headphone jack issue. Nada. I've tried two pairs of brand new Bluetooth headphones and neither one will play out of both ears when connected to this phone. I've tested them on the next model down (iPhone 6 Plus, 16 GB) with no issues and a 5th Gen iPod touch with no issues. I don't think taking it back to the Apple Store will solve anything but that'll be my next course of action if no one has any solutions. I've tried troubleshooting, doing a full DFU, power cycling, wiping both headsets from the phone memory and setting the phone up as a new phone. I have no idea what else I can do, does anyone have any answers?