Amazon.com - My return have not issued

I had applied for a return of a item on **th july it had scheduled pickup on **th july but
on **th July the courier boy calls me and says to contact him personally then he called me with his personal number and said i forgot to pickup you item i would pickup it next day. But he didn't come and i was shown that pick-up has been done while the item is still with me.
Now amazon responding that you sent wrong item to us so we can't refund you

So my concern is how i can send anything if any courier boy didn't come to me.

Amazon averting his mistake on me.

And i have proofs also (call recordings)