apple card - payment declined - what to do?

Hi, I used my Apple Card number from the Wallet to pay on the web for the first time (flight ticket) and the payment was declined. What is the easiest way forward? Isn't there a "customer support chat" option somewhere? Or do I have to call some call center? I was looking around in the Apple Wallet app but couldn't find anything. Most banks have a dedicated support chat button or at least Google can find you some page where they explain what to do. Not so for the Apple Card.

I'll use my normal banking card, but this rejection will cost me money, as I will miss out on the cashback.