Per our delivery and returns policy, if the gift card is invalid a replacement card will be issued to you with no delays or questions. In the case of a gift card returning a message the balance has been used, this will need to be disputed with Steam as we have no control or visibility to which account a gift card was redeemed or when.
Important note: We can only honor and guarantee gift cards for personal consumption. The use or sending of Steam cards to pay for calling services or value transferring to other mediums such as Bitcoin will not be honored by our standard return policy.
If someone is asking you to purchase Steam cards in lieu of services please understand all sales will be final, and you take full responsibility for that 3rd party transaction as well as any issues either party might have with the Steam gift card.