Facebook buyer using uKeshe Pmt Solution Banking detail

1. it does not seem possible to log a direct marketplace issue on the facebook app?? 2. sold a phone on FB, received proof of payment 3. buyer arranged collection via Uber 4. later sends me a message saying that they had paid another amount into my account by mistake will i please refund. 5, first they ask for e-wallet but i decline 6. then i ask for banking details, but would only refund once i confirm deposits into my account 7. next day i check and there is nothing there 8. this buyer rated our transaction on FB but i am unable to access their account 9. I have a number, which i think is a business number but my calls keep getting declined 10. i also have banking details that seem to be for uKeshe Payment Solutions 11. is there some way to contact the buyer via uKeshe? why do they have access to you banking detail? 12. Id provided for Ngenzelokuhle Siyalo Sithole