They can't exchange without the original slip

I bought school shoes for my daughter at Jet The Glen unfortunately the shoes are small.I lost the slip I explain that I lost my slip I dont want tge money back I needed.to change the size they said no they can't help me.Now they are under TFG they no longer under Edcon so they system are not the same they cant help me they even said even if they give me the head office number it won't help because they know about it.I said ok I know the time I came inside the shop to buy can't you trace it they said they can't I went and get a bank statements that showed I paid they said they can't help me I'm so hurt what am I suppose to do with this shoes now where.am I going to get another money to buy her and tomorrow is school this means she's not going.