How Specific a System Prompt Should Be

Two drafts of Desk's instructions cover a customer who says that they were charged twice:

If the message contains "charged twice", check the payment records. If two charges match, request a refund for one of them.

Resolve customer issues fairly and keep customers happy.

Now give both versions this sentence from a customer: "I also think you charged me twice." The first version never applies its rule, because those exact words do not appear. The second asks for a happy customer but never says to read the payment records before making a promise.