Myntra.com — Not accepting my exchange pickup

Address: Gurgaon, Haryana

I had ordered a shoe having size 10 but when i got the product it was unable to fit in foot.So i requested for exchange of size 11. When the delivery boy came he didn't accepted my product by saying that the shoe is stained little black.
The shoes which i ordered were totally white and about the stain which he was talking its little black already when i received the product.
Now myntra is not accepting any call or there is no option to write them. I am stucked please help.