Max Fashion - refund policies

Recently I placed an order in max fashion website. It was purchased for my *-year-old son. by mistake i ordered large size vests (size S ). After product delivery only i noticed that it was the wrong size.
i immediately called customer care and they replied vests are non-returnable items. Actually, I'm not aware it was a non-returnable item while ordering.
To my point, I didn't even open the box to check. It was newly packed and I haven't tried also.
While explaining my concern to your customer person, he requested to mail to "help.in@maxfashion.com" to initiate the refund process. I mailed them but the response is pathetic. They replied as"We regret to inform you that we do not accept returns of personal products such as Lingerie/Undergarments, boxers.
As per our record the product which you have ordered the same has been delivered to you. Hence, we will not be able to take a return request". my question is if i didnt open the package then why not they consider it . They please do the needfull to bring back my refund money