This fraud involves someone offering a product on different Instagram pages. Typically, the products offered are too good to be true as far as the price is concerned. Sometimes you may hear them outright state that they are selling stolen products. Never buy those as even in these cases it is just a way for scammers to get your money and never deliver anything.
How to prevent this kind of fraud from happening: Never buy products in which the seller only receives cryptocurrency as a payment method and promises to deliver products after the payment process is completed.