Selgro in PMB Bought a Sneaker left side is size 4 and right side is size 5

I would like to complain about the Side Step in Selgro PMB, the day before yesterday I bought a Adidas sneakers and told then I want size 5 in store then they gave me size four and they said it will fit me well then when I get home I fit one sneaker and it was too small, then the following day I went to the store with those sneakers to change thee size to size 5, then they said they don't have size 5, then I told them that this sneakers are too small then they took out the insole and said I must wear without the insole and after few days they will fit me good. They I went to home, when I get home I checked left sneaker is size 4 and the right sneaker is size 5. What should I do?