Worst service ever

I bought some items from Yellow Sub Trading last year November and it was never delivered. Then I asked for the refund, and it was paid but not in fully I'm still waiting for the balance. All the time when I call, they will tell me that it was paid, then I asked for the proof of payment to this day I have never received it I'm tired now. I want my money no more discussion . Order no. YST561617