That's interesting to hear. The approval process is seldom through the card company directly, but instead through a portal group such as telecheque services, etc. I know that in some circumstances when cards have a history of exceeding their approved limits, a common 'call' message is tagged to the account which forces the approval portal to transfer the process directly to the card company. This can result in delays or occasionally 'drop outs' where the link time simply failed to complete.
I remember a couple of years ago when I put my card in a cash point in Hing Kong to withdraw some cash. The machine spit out the card with a receipt saying 'my bank had rejected the card.'
In fact, this wasn't the case. It was that the local cashpoint failed to complete the connection to the approval system: but it was easier and a more sound business practice to blame the other bank.
I've used a 'charge card' rather than a credit card for the past eleven years now. Since that time it has been a life-saver as there are no credit limits (per se) associated with the card. Accordingly, there are no 'call tags' attached to the approval portals.
I wish you the best of luck
Fr Bill