Dear [Company Name], I am writing to bring to your attention a billing error on my recent invoice. Upon reviewing my payment records, I noticed that I have made a duplicate payment for the same invoice. I kindly request a refund for the duplicate payment made in the amount of [amount paid]. The payment in question was made on [payment date] through [payment method], and the transaction reference number is [transaction number], which can be found on the attached payment receipt. However, it appears that the same payment was mistakenly processed twice, leading to an overpayment. I believe this oversight could have occurred due to a system error or human error during the payment processing. As a valued customer of your company, I trust that you will promptly rectify this issue and process the refund without any further delay. As per your refund policy, I kindly request the refund to be issued using the same payment method used for the duplicate payment, which is [payment method]. I would appreciate it if you could process the refund as soon as possible, preferably within [number of days or a specific timeframe]. In order to expedite the refund process, I have attached the following supporting documents: 1. Copy of the payment receipt showing the duplicate payment. 2. Any additional relevant payment or invoice documents that may assist you in verifying the duplicate payment made. I would like to acknowledge the excellent customer service I have always received from your company and believe that this matter will be resolved promptly. Should you require any further information or clarification, please do not hesitate to contact me at [your contact information]. I trust that you will acknowledge this request in a timely manner and promptly initiate the refund process. I look forward to receiving the refund without any further inconvenience. Thank you for your immediate attention to this matter. Yours sincerely, [Your Name] [Your Address] [City, State, ZIP] [Email Address] [Phone Number]