Can't return a small item or exchange

I bought a dress on the 30 May 2020 from EarthChild Mall of the south and I couldn't return it due to the pandemic so I went to southgate EarthChild to return the item and I was told it's over 30 days. Why does such a rule apply if u still have a slip and we are still facing a pandemic. I live with my mum who is 62yrs old nd an 8year old, how is one supposed to be going to the malls in such times? This is really unfair, I only go out when I take my mum to get her pension grant money. Now I have an item that's too small nd I can't return it