Myntra.com — Exchange request getting rejected.

Hi,
I ordered one jacket for my 11year child of size which was claimed to be suitable for 12-13Y but it didn't fit him. So I requested for exchange of product with size 14-15Y. Surprisingly, the agent who came to pickup checked the product and said there is stain over it and they can't pick up. I was shocked to get this experience as online shopping has become so common these days. I reached out to customer care and they said it will be exchanged. Immediately after few hours, one agent came but he also did the same and didn't collect the product. Now I have 2 concerns here -
1. If at all Myntra cares so much of product quality check while exchange/return, why does he not do while delivering the product ?
Maybe what they are claiming damaged was always in the same condition when it was delivered.
2. I personally don't think there is any issue with product and my reason for exchange is not product damage but there is a size issue. Why would I put exchange request with another size if I have really damaged the product ? I should have requested in the first attempt for damage product return with right product but I didn't do because I really needed bigger size.
3. Product seller should be caught who claims size suitable for 12-13Y and it doesn't fit even a child of 11Y.

Now I feel like cheated.
Really bad Myntra. You have loose your image of leader for online garment shopping.