Fraud establishment

I made an order from a contractor online, I make a deal to make payment after delivery of the items because of fraud prevalence around which he agreed on. The goods where brought to me while he was not with them, he was directing them and even when the men were complaining about we having to increase the delivery fee because of the distance, we called the contractor to let him know and he called them immediately to sort them and they delivered the goods. Afterwards, we made payment to the contractor account and the people who delivered the goods left. Only for them to come back about an hour later to say they were duped and he never pay them, he ordered from them as well which personally I think it's not logical how they would deliver a goods and go without payment. I will like to know what the law says about this please. Thank you