[Name, Company Name & Address here]
This is to inform you that as per our discussion on [date], we are returning the [product name] to you.
Instead of refunding the payment made by us for these products, we request you to please credit this amount to our outstanding balance with your company.
As per our records, the credit amount should be $[credit amount]. Please advise that whether this amount is accurate, according to your records.
[Your name & Designation]
Encl: [Enclosures List here]