Follow Up Letter Regarding Credit Due –
[Name, Company Name & Address here]
This is in reference to our last order [order no.] dated.
We ordered for [product name], under invoice [invoice no.], for the amount of $[amount].
We have returned the goods to you in an unused condition on [date]. At that time, you assured that you would refund us the payment made for these goods. Please note that we have not received any payment from you till date.
So, please arrange the payment for these returned gods.
Thank you for your prompt attention.
[Your name & Designation]
Encl: [Enclosures List here]