chup chap lelo . com has sent me wrong number of shoes which is entirely thier mistake but not ready to take or replace the goods

On the 27th of jan i ordered a pair of Air shoes number 9 from chup chap lelo .com, i recieved my order on 4th feb and that is when i discovered that the shoes they have sent me differs in size, I had ordered number 9 and recieved number 10..i tried calling thier costumer care number which is forever not reachable .. Then i sent them a mail regarding the same , firstly they said ok we will check and arrange a call back in next 72hrs, post that there was no sign of them getting back, i again mailed them, and then they said you have recieved a number 9 shoes as its written on your order number so how are we suppose to take your complain, i explained them and also sent them product and bills images.. The problem was that the order number has the number 9 shoes, but inside on the product it was written number 10.. Now they say that as they have no pick ups available in my area, i should pack the product and courier it to thier noida office.. And if they dont recieve back thier product within 10days they wont accept it back..Im extremely unhappy with thier careless carefree attitude.. I want my product replaced or my money back asap.. Thanks