If you canceled the transaction before it was posted to the bank, no charge was processed.
However, your buyer may see a “virtual” charge on their account corresponding to the authorization request.
When a credit card transaction is canceled, the platform sends a reversal request to cancel the authorization request.
If the card issuer accepts the request, the authorization limit of the cardholder’s card is restored.
Otherwise, or if the acquirer does not support the reversal, the transaction is canceled and the card limit is restored when the authorization request expires.
In this case, your buyer must wait until the authorization request expires.