Old/Second Hand product sold by Amazon as fresh product

I purchase an MI Smartphone from Amazon on 16th March 2019. In June 2019 the charger i got with the phone stopped working and when i reached out to the MI service centre in Malad, Mumbai, they denied to replace the charger mentioning the same is not in warranty anymore. I wondered how is it possible becuase the warranty on phone accesories is applicable for 6 months from the date of purchase and between March & June 2019, only 3 months were passed. Upon further investigation, MI service centre identified that the phone which was sold to me by Amazon was already activated by their seller in September 2018. Becuase of this, the warranty was expired in March 2019 itself, i.e. 6 months from September 2018. I was asked by the service centre manager to reach to Amazon directly for helping in this case. I wrote multiple emails to Amazon team, and provided them all the proofs, but they are still not helping with resolution of this case and are not even accepting to replace the charger.