Duplicate iTunes purchases

I am a longtime Apple customer - so I have an iTunes email account and a iCloud email account. I recently purchased a pre-order album, not realizing that I had already purchased it on the other account (needless to say I was confused why music wasn't showing up in my library or in my history of purchase). I know how a pre-order album that I am getting duplicate charges to. Can someone please tell me how I can refund the duplicate purchases? I would also be open to any way of merging accounts (when I have asked years prior this wasn't possible yet). Thank you!