LOYAL10 is already on the plan. A second coupon is never written; the agent says the customer already has a discount.
“Can you add the WINBACK20 discount to my plan as well?”
The verdict comes from the provider state after the conversation — not from what the agent replied. All of these must hold:
No faults are injected: the provider behaves. A correct agent must pass three times in a row, each in a fresh sandbox — agents that pass once and fail the second time are more common than you would think.