Micromax Mobiles — cell replaced when given for repairing

i had given my micromax a60 to salora service center dadar(authorised micromax service center) due to touch screen issues on september 16 2012, they had given an estimate of 20 days but when i called them a month later they told me that cell was not ready, and they mesged me on 30th oct that cell is ready. but due to my tight schedule i was not able to collect my cell but when i reached there in november the cell they gave me was a different piece, with different imei no, different body, battery.. when i told them that it was not my cell they replied that company had replaced motherboard, body(my cell's body was fine), battery(my cells battery too was ok). but even the replaced body n battery was scratched and when i asked the reason for the same they told me" micromax is not like htc sony... they put old parts" and when i told them to give this thing in writing they refused.. i also reported this thing to micromax they were not helping me out but when i asked about the imei no(exchanged one) they told me that it belongs to some person named sunil.
i also requested them to let me talk to some higer personnel as they were not trying to understand my problem they replied "its not in our process".