If you paid through Omise (i.e. using your bank card), it may take up to 45 days for the refund to reach your account.
Please note that many banks will not notify you when a refund reaches your account. Please check directly with the bank to make sure you have received it.
If a full refund was sent to you less than 24 hours after the initial payment, no transaction will occur in the first place and no funds will be taken from your account at all. Probably, you will not be notified about the refund by your bank.