The customer service job is not a nine-to-five job. This job would require flexibility, and the interviewer will ask you this question to assess how flexible you are with your timings. The more flexible you are, the more chances you have to get hired. Say yes, if you are okay working a rotational shift and on your weekends, and if not, back it up with a valid reason. They might consider that at times. If you cannot work on weekends or 24*7 shifts, you can tell them you do not have a problem working on weekends, but you have recently enrolled in a management program that would require your attention on weekends. However, you can work on weekdays. This question is a regular feature in interviews for call centers, be ready to tackle it.