As a general rule, yes, assuming that your order is not more than 30 days old. Simply buy the licence for the font you want to use. Send them both your new and your old order reference number and they will cancel the order placed in error. Your money will be refunded. Your new purchase must be of a similar product at a comparable price. You will need to delete the font you purchased by mistake as the licence for this font will be cancelled, meaning that you are no longer authorised to use it.