When I sold Saab vehicles years ago, we had an agreement between salespeople. Since no one could reasonably expect to work 12 hours a day, six days a week, there would be times when we would have to cover for each other.
On one occasion a client to whom I had shown no fewer than 5 vehicles finally came in, ready to buy. On previous occasions when he would walk in, my sales partner would look up and say "Jeremy, you're guy is here." However on this, my evening off, he came in and she sold him a very nice car, kept the commission and took credit for the sale. Her explanation? He didn't ask for me.
When I approached the dealer principal, he told me it was my problem. "No," I said. "It's yours. If she's stealing from my family, she's stealing from you." Several months later she was fired from the Saab dealership for dishonesty and misuse of company property.
I'm pretty keen on sales people telling the truth. If they'll lie to a customer, they'll lie to their employer.
If a salesperson is too embarrassed by the truth - either of their own lack of ability or of the shortcomings of the product they sell, they need to find new employment and maybe even a new career.
And that's the truth.