You are one of our most valued accounts and it is with deep regret that I must advise you of a change in your account credit status.
From now on, it will be necessary that a cheque accompany each order for merchandise from your firm. We must insist upon this until your account is brought up to date, at which time we will reevaluate your open account status.
I know this will represent an inconvenience to you and I hope that this will not interfere with our long and profitable relationship.
We value your business and look forward to resolving this difficulty in the immediate future. If I may be of further assistance please call me at your convenience.