Because the amount already billed will not change even if there is a refund, this amount will be restored to the credit card limit, so when the user repays, the bill amount will be more than the actual amount, but the refunded amount does not need to be repaid.

So users can know what causes the inconsistency between the bill amount and the actual consumption amount as long as they check the bill once.

If you don't know, you can call the bank's customer service number and ask the bank to inquire about the source of the extra money. If the amount is large, the user can submit it to the bank for processing or call the police.