Help with bitcoin

Not like im new but i sent a 120$ payment recently and it seemed to say "Double Spend" and now it shows this https://blockchain.info/tx/6d37717dc...fa3e719012860d what is wrong? Apparently my customer didn't get his refund so i had to send him more money. Its not even back in my own wallet. I use Block chain and i used a .50$ fee for a 120$ payment. Anyway i can recover it or know where it was sent?

Apparently that payment was not included in the blocks. Don't send him more money, both transactions may go through.

It would be back into your wallet if it's not included in the blocks. Try contacting blockchain.info support