If you make a single purchase or are refunded but notice a double charge on your bank statement, don't worry, this is most likely an authorization (pending charge), rather than a hard charge.
For example, when making a payment by credit card for certain services, your credit card company may authorize your card before the actual funds are taken. If this is the case, the authorization appears on your bank statement in addition to the actual charge. But don't worry, as the authorization charge should disappear from your bank account within 3-5 business days.
For refunds, you may see the refund as a pending charge, that is more than likely an authorization that will fall off of your account once the bank completes processing of the refund.
Of course, feel free to reach out to our support team at support@mdacne.com if we can provide further clarity regarding any charges on your account.