Filling to contact customer

I bought winter clothes on the 1st of May 2020 on level 4 for my daughter, the clothes were small for her so I went back to the store the following day to do exchange they said I cannot do exchange due to corona virus, they said they are following mandate from head office. So I did got call of thier customer service office, the lady that I did speak to her she said she will check with mall of the North branch and then she will contact afterwards. So I went to jet on 08 June to if i an get my refund they said according to policy refund is done within 30 days after those days they cannot do that, after they failed to do exchange. So what must I do with this staff that I bought from them.