Homeshop18 — ragarding my order no[protected]

my order no is[protected]..they insures me that product is good and it will fit it to my window but when i recieved that item is very small in size.when i call him for replace then they are telling me that is against his rule.my question is why u assures me to buy and why u have not told me that product deliver will no be replaced.i want my money back or i want larger cooler from that if the larger cooler is costlier then that i will pay the rest amount