Sample letter inviting criticism from the customers regarding the goods

COMPANY
Address
Date

Dear Sirs,

We note with regret that you have not assigned us with any business since October last. Naturally we are searching what the cause may be. If there were anything wrong about the last order, will you not let us know? We want your future business and cannot allow the past to remain in such an unsatisfactory state. We look forward to an opportunity to adjust our errors, if any, and we trust that your original confidence in the past should be continued to us in future.

Yours faithfully,

(Name)