Asus — Service Center Issue

Address: Pune, Maharashtra

I submitted my fonepad before 20 days to service center regarding battery backup and heating issue then after 8 days they called me to pick my phone as it was ready. so went there pick my phone and came back to home and what get to know is my device has only 4gb inbuilt memory(its suppose to be 8 gb) so i called them again, but they were not in condition to accept the fact so i went again there and i taut with the manager, and i was agreed with the mistake done by technical person and told me again i need to kept my phone there and they will call me when it will ready but after 8 days of waiting i again called them today. But 1st person told me that we do not receive the part yet so i need to wait. After some time same person told we received your part yesterday but it was faulty so they told me we order again and let you know but when ask the person that i wants to talk to your manager then firstly he refuses my request but after some time he agree with that. When i taut with manger he told me we do not receive the part yet, it will take time so ask them, its your problem i need my device as early as possible or replace my whole device as it is in under warranty..but he refuses the same...same day in the evening he called me and told me that my device is ready..how it is possible if they didn't receive any part of my device. But still i accept that and ask them to deliver me at my place..but they told me my device will not able to update to new operating system (earlier was didn't have this issue) ...still they didn't reply. I don't know what to do? please help me