Amazon India - Suspicious sale of Nokia phone

I bought a Nokia *.* mobile phone from Amazon on *th October ****. After couple of weeks, the phone went dead. As the official return window had closed by then, I took it to the nearest Nokia authorised service centre. To my shock I was told that the date of activation as per their record and the date of invoice as generated by Amazon differ. I was told that probably I have been sold an used phone instead of new. I have been writing ever since to Amazon. However the keep seeking more and more time despite passage of more than five months since.