Amazon India — Refund rejected by amazon

I have returned the reebok tights after a regular follow up for many days with their escalation department they raised an investigation for which they have asked to call me after 3 days after 3 days when i have called they said i haven’t returned the original product they’ve sent how would i know on what basis they’ve conducted this investigation and if they’re so particular there shouldn’t be any option like received wrong item while creating returns. I have returned the original item now they have kept the product also and not refunding my amount. I have been there regular and valued customer from so many years and they’re doing this to me. Pathetic please help me get my refund.