I'm not sure how to approach this situation where customers claimed they've been charged twice for a transaction that failed (not declined) the first time. Usually when the transaction fails, the printout would say ''communication error, chip malfunction or service not allowed.'' However if the customer looks on their mobile banking and/or call their bank representative at that moment, it will confirm a transaction took place. Now I know that transactions will appear as temporary authorizations and will need a few days to settle correctly. However I can't convince them that they haven't been charged twice and therefore I do not need to refund them money.