I have been using zero b table top purifier for the past 3 years. I did not find any problem in these three years and so surprised to see this comment about their service.
I have recommended zero b purifier too a lot of my friends and I think they did not face such issue as I would have come to know. I would recommend you to speak to their ho service head and get this issue resolved.
I havent received any bad service from them yes some times there was delay of one or two days in technician coming for the normal amc servicing.i wish your problem get resolved soon. all the best