Shoe size to small but can't exchange for correct size ***

I am writing this review as a disappointment and unhappy customer. I bought my son slides on the online shop ,my son is a size 6 . The slides are small meaning they are a small cut / make and I would have to get a bigger size. I called one of the stores and the customer service number and was told the shoes can not change them for me as they where on special. How is that so ? All I want is to just exchange the shoe for a size that will fit my son, not that I want a refund. What am I suppose to do with these shoes now , I bought them as my son newdethem by Saturday. I used my hard earned money to buy from a reputable company but now I feel I am being taken for a ride needing robed.