Help!!! He Has Refused To Return My Money

Hello nairalanders. I need your help and contributions concerning this issue. Had to open a new account for this. Please take your time to read through.
At exactly 3 weeks ago, i made a terrible mistake by sending an amount (#53,000) to a wrong account number.
Immediately, I put a call through to my bank to help reverse the transaction but couldn't reach the customer care representative. I tried several times but exhausted all my credits waiting on the line for someone to pick up. I sent mails and tweets, yet no postive response either. 
After about 3 hours i was able to speak with a customer care rep. I explained everything to her, she did a background check, confirmed the transaction but sadly, it was already late, she said the recipient had fully withdrawn the money. My head went blank immediately I heard that. She said they have a team that works on such, and that they will get back to me. 
I did a check on the account number i wrongly sent the money to and then I realized it was a nairalander, whom I once paid for his service sometime around middle of this year. I do not know him in person. Then I started searching through for his contacts and luckily I got one. I put a call to him, tried explaining myself but from his tone I realised one would require a long conversation, and also for evidence purposes, I decided to resort to whatsapp. The following are the conversations with him.