Disappointed customer

I'm so hurt I went to rage yesterday in rustenburg purchased shoes for my daughter only to realize they are small I lost my purse tht day in town along with the slip I used my bank card to make a purchase so this morning I went the to exchange the shoes from size 10 to 11 I explained I lost the slip I can provide them with my bank statement to show the transaction ND woow I was told that is not possible now I asked what do I do because I don't have the slip the lady asked me to step outside of the their shop while I still figure out how I can get the slip I'm so disappointed because I shop at rage all the time fore and my daughter I'm not asking for a refund just a bigger size now if the shop won't help me who will should I just put the shoes at home. Ple Please assist with this matter