Amazon - No action taken despite of regular calls

I had ordered a Samsung mobile(Galaxy M**) on *th February(Order# ***-*******-*******), which I had to return due to performance issues. Amazon straightaway denied the return and instead offered a replacement. I availed their replacement offer, and the pick-up guy had to visit my house for receiving the item on **th of February(Order# ***-*******-*******). Now, the pick-up guy had arrived at my house on **th Feb, at around * p.m. and I had handed over the phone to him, since it was the day for pick-up. But then another pick-up guy arrived at *:** p.m., on the same day and asked for the mobile, for which I told I had already given it to the person who came to pick it up at * p.m. Next thing amazon did was label my replacement as "Rejected by the Customer". From that day onwards I've had more than ** calls with amazon's customer service and numerous chats on their website, but all I get in reply is "Your issue is being investigated, please wait for *-* business days". It has been more than a month and that was my younger brother's phone which he used for his online classes and assignments. I have co-operated with amazon in all ways possible, also by providing them with details of the pick-up guys(which were recorded by society guard for entrance).I have never experienced such pathetic service from such a famed brand. FYI, I have been a loyal amazon customer since **** and bought tons of products every month since then and never had to experience such a painful phase. This past month has been miserably inconvenient for me and my brother all because of Amazon. I just want my money back. Please, I am fed up of this.