Amazon India — refund not done as per telephonic conversation

Address:

A/101 Suryakiran chs ltd, S.T Depot road nallasopara west

I bought refurbished mobile xiaomi redmi 4 which delivered on 24 july phone has microphone issue it is not working on call, if i put it on speak then only my voice can hear who is on other side i discuss about it with customer care on 1 augest and 2 augest, they told me to update phone, so did it, but then only it was not working, again i call them so another technical supportes says to install blanco app to check Phone, i did it and call them to ask about pin code then they said me your phone problem can not catch by app,
So i ask them for replacement or refund then he said right now we don't have this product we will refund you in 2 days, and its is not done yet. And not i call them for refund status then they are saying it is not possible now, you can check all recordings, please try to understand us, refund as early as possible, its a humble request