No Exchange

Me and my husband went to Musica Middleburg to buy 3 disc after an hour we noticed one disc was incorrect we went to the store to exchange but we could not find the invoice inside the plastic bag the cashier claimed to have put it inside but we could not find it now we are sitting with a cd we don't need and no one is willing to assist us or do a reprint or even reverse the cameras, instead the manager told us it is our loss to think she saw us and assisted us all we want is to exchange with a correct one thats all.