Simply replace the unfilled areas such as "[]" and "[date]" with your information.
Dear [Vendor],
We are experiencing a problem with the [product] we have purchased from you. The [product] has been [issue]. This problem is severely affecting our [production/ productivity] and therefore it is negatively impacting our revenue.
We require that you immediately address this issue. We expect that you will send a representative to our facility in order to solve the problem. We are putting a hold on all payments to your company until this situation is corrected.
We understand that your representative will need full access to the [product]. As this will further impact our business, we need to plan accordingly. Please contact us right away so that we can schedule this work.
Sincerely,