Amazon India - Defective Product Recieved

I have purchased a I-Phone SE **GB Rose gold model in OCT-**** through Amazon.in, In Jan-**** phone hanged and it automatically goes into switch on & switch off loop. I contacted apple care center B*X Udaipur, They diagnosed the phone and told me that it was already been repaired and denied to give warranty on the phone.
I contacted AMAZON on this issue they agreed for refund on **/**/**** at **:**am throgh official mail and after few hours they mailed me that they will not refund any money and i hv eto go for paid services.
Why should i pay as my phone is in warranty?
Amazon sold me a defective phone on account of new.