1. The person in whose name the card is made out is responsible for all transactions from that card. ie if you have a UBS company card the fact that UBS are simultaneously the (quasi)issuer and the owner of the card is irrelevant when it comes down to ultimate responsibility for payment from transactions.
2. The only time when the issuer actually takes responsibility for the transactions is when the credit card is reported missing/stolen before the transaction occurs or as soon as possible after it is stolen/goes missing.
3. Which of course means that if you can reasonably prove that you did not make the transaction because, for example you could prove you were on an aeroplane using your card when your "card" was also used in Migros, then the responsibility for the loss goes to the retailer.
Also note that a credit card transaction does not require a signature!