You’re not a customer-service representative, you’re a salesperson. And it’s not the job of a salesperson to tell a customer that he’s right. When you call a company for support, on the other hand, you expect the customer-service rep to help you get the outcome you need.

But if you’re a salesperson, acting like a customer-service rep will make you weak and ineffective (or what we would call an “order-taker”). Your relationship with your client is different. It confers greater responsibility, and this often means you have to tell your client that she’s wrong or that she can’t have what she wants the way that she wants it.

Dear client, you are wrong. If you’re a salesperson, you want to be consultative. You want to achieve “trusted advisor” status. You want to create the highest level of value, which means you’re setting the bar very high for yourself.

Your client doesn’t know what he doesn’t know. He doesn’t know what other companies are doing. He doesn’t know what you’re doing for your other clients. Most of the time, he doesn’t know all the options for producing better results. And a big part of the reason he doesn’t know is because he doesn’t know that he should be dissatisfied.

You have to tell your client that what he believes is not true, when that is the case. You have to tell him the truth about how he can produce better results. And you have to tell him how he can do better, which brings us to the second part of your responsibility.

Dear client, you can’t have what you want. Your clients can have anything they want, provided they are willing to do what is necessary. If it were up to them, most of them would want the better results you promise without making the changes they need to make and without investing a penny more than they are investing now.

You do your clients a disservice, however, when you allow them to believe that they can have what they want without changing what needs to be changed. You have to tell your clients what needs to change, why it needs to change and how it needs to change. You aren’t helping your clients by allowing them to believe that they can have what they want without investing more. You have to tell them why they need to spend more and what that spending will get them. That’s helping them. Letting them believe a lie is not.

If you want to be consultative, trusted advisor—a peer—then you can’t act like a customer-service representative. You need to be liked, which means you need to do all this with a good spirit, and you need to be trusted, which means you cannot shy away from talking about the tough issues. Remember: You aren’t going to lose your relationships by tackling these issues. But you might lose your relationships by avoiding them.

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S. Anthony Iannarino is the managing director of B2B Sales Coach & Consultancy, a boutique sales coaching and consulting company, and an adjunct faculty member at CapitalUniversity’s School of Management and Leadership. For more information, go http://thesalesblog.com/s-anthony-iannarino/.