Dear

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 check 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.