I've e-mailed both four times, no response from either.

I'm in Australia and purchased a pair of Nike trainers on line from cheapniketrainers.co.uk on the 27th August 2017. I received an e-mail from a third party, onlinescredit.com. They said my purchase was successful and transferred the equivalent in pounds of the price of the trainers. Thinking that odd, I checked the original site and there appears to be no record of my purchase. I've now e-mailed them and the third party 4 times without any response. Anyone help, please?