Jabong.com — not returning the package

I have ordered a jeans from jabong.com
As it was not fitting i had to request for return. So when i put the request the delivery executive said, as there are no serial no we will no tr be able to return it. Same words were said by the jabong.com that will not be able to process return as i have lost the serial no which has been given by jabong.com (Told by jabong). But why will i even loose the serial no if i know it will be useful.

They are saying that they won't be able to return it as i don't have the barcode. I have everything the jeans is not used and i tr consists of mrp tag and everything. Guys don't shop from jabong.com at it will play with your hard earned money.