A Call Center Agent position requires certain technical knowledge and skills (typing speed, computer knowledge, database knowledge, etc.) but it is also true that the right attitude is mandatory in order to get this kind of job.
Check your level of technical knowledge and skill, you will most likely have to bring it up at some point in the interview (what is the average number of phone call you can make a day? What applications are you familiar with?).
However, it is not all technical-related questions, matter of fact, most questions during the interview have to do with your job-related competency and aptitude; the following questions are some examples:
What can you tell me about yourself?
Here you can go for a brief talk about who you are, and why you are applying for the job. Keep it professional and mention how much you like interacting with people.
What was your experience in your previous call-center job like?
Here you need to focus on your labor towards helping people. Mention your functions and duties, and mentioning how you enjoyed working with other people (co-workers) will give you some extra points.
What software applications are you familiar with?
Ok, a question about technical knowledge. Interviewers will most likely consider someone who is familiar with call-center programs and data bases as a more serious candidate since they would be able to save up a lot of training time. Make a list (or simply check your CV) of all the applications and data base knowledge you have. Do not leave any details behind; even regular computer software will be kept into account.
What do you think about team work?
In most customer-service jobs, interaction among co-workers is common. Employers will always consider communication and cooperation as basic requirements for the posted position.
Why do you want to work with us?
Mention your interest in working for the company but remember that you may have to support your reasons. Do not forget to mention how you feel your skills would perfectly fit the company needs. For interviewers it is important to know how long employees want to stay for, so be honest about it and if you are looking for a long-term job let them know.
Some research about the company will be needed if you want to keep up with this question.