Clovia.com — Returning back the wrongly sent item

Address:	Clovia
Website:	Clovia

I have made a purchase at two websites simultaneously
Clovia and Little box.
They both share same logistics -Xpressbee
Due to size mismatch i had to return(replace) both companies item. But due to same logistics, confusion was created and i for clovia order ID: 16269976, i sent Little box item which was worth 2000.
From past 1 month ( infact more than 1 month) i hace been trying to contact clovia but they are not helping and only telling that they did not receive the return item to their ware house which is quite impossible given the time frame.

They are now not returning my product and holding it and not even responding to mails.