Thank you for sending 'Call-Center' to Shimmer, we appreciated the chance to read your work. Unfortunately, however, it isn't quite right for us. I did enjoy it, and thought that it was well-written, and interesting, and I liked the dark humor, but we do receive loads of zombie stories and I felt that this didn't really offer anything new (especially as it's very similar in parts to a story that we've already accepted for the next issue). While it's not for us then, all the best in finding a home for it elsewhere, and do continue to send your work our way.
Good luck with your writing!