Yu Televentures — yureka plus dead after update

My yureka plus device has got a notification regarding the update to lollipop. I clicked on update since my friend told me he also got the same notification and after update, his device got volte feature. My phone started downloading the firmware and then rebooted. But the device didn't start after completion of installation. I've contacted the yu support team and they have given the authorised center. Since the device is in warranty, they sent the device to company on 11th of november but didn't get any update regarding this. Initially they promised device will be returned by 27th of last month. Authorised center people keep saying please come next week.