The seller can accept or refuse your cancellation.
As you have paid, they will either cancel and refund you or send the shoes.
If the shoes arrive and they are fake, you will have to return them using the Money Back Guarantee.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)