"Are you the same person I was talking to earlier?" followed by "nothing" in response to "what" could be creepy if it means the support person wanted to continue the conversation in a more personal way if the response had been "yes" instead of "what", probably using a different messaging system because they found something attractive about the user via their conversation; however, it could also be the support person was wanting to understand if the new CC number would have the same problem as the old one if they had this conversation with the same contact, earlier, and there was less of a chance that the transaction would go through so someone might need to monitor it more closely. It could also be the support person doing some sort of fraud detection if they had just had a similar conversation and wondered if someone was trying to validate stolen credit-card numbers by trying them one-by-one. Maybe the name or address of the CC number was different than the previous card. The lack of explanation by the support person about why they'd asked the question, might be creepy, but it would also make sense they can't explain if they are doing fraud detection or if they will escalate the monitoring to a different level as that is an internal process they aren't allowed to discuss.
In short, I can see how the interaction might be viewed as creepy but there might also be a reasonable explanation. In any case, all conversations are recorded and the support person would likely eventually get into trouble if they were being creepy and they'd know this so that's why I think the question was about something else.