Could someone please help me on how to answer 'What is your greatest accomplishment?'. I have an interview for a Customer Service Consultant position and I don't have any experience.

Is there an accomplishment in your past that has to do with helping someone, having empathy, showing that you went to the nth degree to solve someone's problem?

Not that I can really think of. Could you please give an example?

Generally an employer is trying to see where you have applied yourself, and gauge what life experiences you do have, and are you confident and willing to learn. So let me ask your age, and what have you been doing for the last 3 years. This may give some insights to help suggest a good answer to this question.

Ok, I'm 19 and I recently left post secondary school

Not that I can really think of. Could you please give an example?
Have you gone above and beyond at home, willingly helping parents with major chores? Have you helped disabled people in any way? Are you part of a church group or youth group that helps people in various ways?

Continuing your education after high school is a perfect answer to this question. Having a specific goal is even better, like a certification or degree. What kind of job are you interviewing for? Does it have anything in common with your secondary school experience?

Thank you, now I have an idea if what I'm going to say