Mal functioning of Mts data card no.8433134129

My data card no.8433134129,esn no.Dd178fc1,365 day-plan bought on 2108/2011.Worked well for 8.5 months,stopped functioning from 15/5/12,I was given replacement on 16/5 but that also DID not work.Again on 17/5 I deposited the device with borivali service centre vide wo no.Fln/Zm/12/00054 dtd.17/5.Replacement of which I recd.0n 31/5 which also stopped functioning since evening of 16/6.I was harassed by the cervice centre for 15 days with 15 days' business loss +physical & mental torture.Now,I am going to deposit the device with kandivali-west gallery from where I had bought !I had lodged the complaint on your site but even after a month nobody has bothered to reply.In the meanwhile new device has also failed !could anyone help me ? I am really repenting for buying your product !pls reply me at @rediffmail.Com for further course of action ?