If Bitrefill gave you invalid giftcards then they must refund you without waiting for Amazon to refund them.
You would hope so but there might well be something buried in their terms and conditions. They might try to claim the contract is between you and Amazon and all they did is provide a way of paying for the card.
Even then I wouldn't regard that as good enough and would expect some good will.
Just finished reading their Terms of Service.
Appears to me I should be eligible for a refund.