Lenovo — received damaged motherboard mobile

Address:

Chittoor, Andhra Pradesh, 517002

I have purchased lenovo k8 note 64gb mobile for 13998/- in amazon flash sale on august 18, 2017 which was delivered on august 22, 2017. I haven't used the mobile much as i have lenovo vibe k4 note too. But now when i started using the mobile, it worked well till jan 06, 2018. Suddenly from jan 07, 2018 the mobile was getting restarted on its own and wont boot at all. When i took it to lenovo care center, they told it might be software update problem and when they opened the back panel of the mobile, we came to know that the motherboard was a damaged one and it was repaired before it was bought by me in the sale. Hence they told me it won't come under warranty and it would be charged for an estimate of 2750/- which is unfair as it's not my fault to get such a wrong product. I need the item to be replaced as amazon authorities were not responding properly and iam in the state of loosing my whole money.