Deloitte's survival depends on client satisfaction and exceptional service and performance. This question allows you to speak to your work ethic and commitment to the team and customers and provides insight into whether you do the bare minimum or are willing to put forth some extra effort when called upon. The interviewer wants to understand who you are, your approach to customer service and whether you will effectively represent their brand.
Before your interview, dedicate time to researching Deloitte's website, media coverage of the company, interviews with the executives, how they compare to their competitors, and client and employee reviews. What are their clients saying? Note recurring keywords on their website regarding their customer service standards and core values. Speak confidently about how you plan to uphold their strong customer service standards if given the opportunity.