Take them to small claims court...you shouldn't need a lawyer. However, if they don't live in your country, you're probably wasting your time unless it is a huge amount...you'd have to sue them in their own country and there is no guarantee that even if you win a default judgment that they will ever pay.
If it is indeed a matter of being scammed, this would be a criminal, not a civil case, so you should contact the police first and go from there. You could also just email them a threat that unless they refund you within x days, you will contact the police with their payment information.
Also, you might want to start the conversation with Payoneer to see what legal remedies you might have there. Good luck.