Unhappy customer

I purchased a dress and shoes at identity Lydenburg i got home and find that the belt that comes with the dress is too small amd does not fo arround my waist therefore i am not able to wear the dress i removed the tag when i wanted to wear the dress but didn't throuw it away unfortunately i lost my slip and wanted to return the items but was told thet can not assist me to do an exchange without a slip because it was a cash sale and not on account i only wanted to exchange the items for something else as i will not be able to wear the dress since the belt does not fit. My question is other shops does asssit when one loses their slip why identity is having a lot of excuses i am not a happy customer because i am now stuck with a R500 dress that i can not wear