Advance payment to a supplier but he didn't supply the goods

I had made an advance payment to a supplier, but he didn't supply the goods and didn't return my advance money. So, the agent who introduced me to the supplier, he promised to refund my advance money. I purchased the goods of similar value from a different supplier, through the same agent and asked the agent to pay to this supplier the amount that I had paid as advance to the defaulting supplier, he relented and did as instructed. Now, how to legally bar the agent from making any outstanding payment claims on me.