Simply replace the unfilled areas such as "" and "[date]" with your information.
It has been our policy in the past to supply customers on credit, but owing to tightening economic conditions we've had to revise our policies as follows:
1. If the customer is more than 15 days late on their monthly payment, shipments will be suspended for that month. To keep our supply liquid we need to keep our cash flow similarly liquid.
2. There will be a surcharge of [amount] on accounts falling more than 30 days behind.
While I am sorry that we must enact these measures, I am afraid that there is no alternative.
Our company policy is, and always has been, to provide the best service available to our customers. We hope you can appreciate these necessary policies going forward.