Irikefe Aniboh billed me over $1500 USD in work performed for someone else

Irikefe originally was hired by me on a freelancer platform to perform some machine learning research. His work was average however I accepted it and paid him. A few months later he billed me (perhaps not intentionally) for work he was doing with another client, this went on over 2 months and I had not noticed.

When I finally did I approached him about it and it seemed at the time to be a genuine mistake and he would refund me. Many months later this is not the case. He protrays himself to be an educated professional however he has not acted as one.