Is there a way to get cashback with a visa or amex gift card??

I have some unused gift cards of visa and amex, so can i just go to a grocery store and ask for them to charge the card and give me cashback like they would a debit card?

another trick is transfer balance from one card to another
call second company and tell them it was mistake, and you want your money back. if they say we can only transfer it back tel them your account with them is closed or you cleared their balance by direct debit.
they will send you a cheque.
thats how we do with credit card companies in UK