Buyer gave me a negative review for shoes that did not fit and now claims the purchase was unauthorized.

I just received my first negative review on EBay. The buyer claimed the shoes are two sizes too big. The shoes are a 7.5 which the box and shoes state. I wear a size 7.5 and they fit me perfectly, however, I didn’t care for the color. The buyer never reached out to me but instead gave me a negative review that they did not fit. Now the buyer is disputing the charger claiming they never authorized the purchase. Should I reach out to EBay and make them aware that this buyer is attempting to commit fraud or is it just a waste of time? Thanks in advance for taking you time to read me whining.