If you attempted a transaction and it was declined by the merchant but is showing up on your KOHO transaction feed, this is typically due to an issue with the merchant's payment terminal. Typically, these transactions will expire and the amount will return to your account in 5 business days.
However, if you find that the charge is showing as 'settled' on your account (you can find the status in-app by clicking on the charge in your activity feed), please reach out to the merchant first to arrange a refund.