Worst service and non return of my recieved product

I had bought covers of sony xperia z ultra worth Rs 800 from amazon. in .Just as they send the product,my mobile got cracked and i had called Amazon to return the same,but they told as it has been dispatched,after recieving the product we will take return of the same.After that they had booked the return for 4consecutive days via some courrier service,but till today that is 11th september 2015,no one has come to collect the same.I had received the same on 3rd september 2015.Everytime they kept me waiting for them by leaving my work.Now what should I do?they had became fraud totally.Im helpless.