Customer service does not always mean sales. The interviewer wants to know that you would be comfortable taking a customer inquiry and turning it into a sales opportunity. If you have a specific example of a time when you made this happen, this is an excellent addition to your reply. Be sure to mention any training that you have in sales, upselling, or a similar skill.
"I have a few years of experience selling in a telemarketing environment where upselling was very important. I am fully comfortable putting in some extra time to turn a customer inquiry into a new sale."
"I have not received any sales training, but with a little bit of help, I think that is a task I would enjoy. I am great with building customer relationships."
"I believe that each customer service interaction should be considered an opportunity to upsell or turn an existing customer into a larger one. I am very comfortable doing so when I can stand behind the product that I represent."
"I will upsell a client any time that it makes sense. It's important to me that my client trust my recommendations so, for that reason, if they upsell opportunity is relevant, I will certainly take it."
"In retail, I consider every customer interaction an opportunity to sell and upsell. Its important to me that the people I communicate with are aware of the great products and services available to them. I am happy to make suggestions that I believe will benefit their lives."
"I am comfortable selling, and upselling, anytime that it makes sense. As a sales professional, I have a natural inclination to take a customers' pain point and turn it into an opportunity to help them through a service or product offering."