I asked if he could train my Golurk to level 9k. He agreed for 105B exp, which was 15 Shinies and 750 coins. (His rates)

He only did about 14B or so, and I messaged him saying if I could just take back the 15 Shinies and 400 coins, because he only trained 350 coins worth, (again his rates).

He's not responding to any of my messages, and won't complete the trades I send him. He's been online, but when I check my outbox for the messages I sent, he hasn't read ANY of them.

I have messages and a little video for proof if need be. The only reason I took Golurk back so early was because I didn't know how slow he'd be. And he even agreed to the refund and said something along the lines of "Okay, and just let me know if you need more training!"

In conclusion, I would just like 15 Base Shinies and 400 coins back.

No, it's not a 'if need be.'
You ALWAYS need proof.
No proof = No ban/warning.