There's no reason why you shouldn't hire me because I have skills and qualifications that your company have been looking for.
Why Should We Not Hire You, As A Call Center Agent?
This seems a very strange question to be asked in an interview for a job - probably it's a test to see how strong your self-confidence is, because I imagine you need plenty of that to work in a call centre.
I suggest replying with an affirmation that they should indeed hire you, a list of all the skills and strengths you have to offer their company, and an affirmation that you want the job they are offering.
I suggest replying with an affirmation that they should indeed hire you, a list of all the skills and strengths you have to offer their company, and an affirmation that you want the job they are offering.