Complaint to Pep stores

I bought white shorts on Monday 29th and they could not fit my kids then returned them back for my cash back and they still have tags on but no slip and they completely refused to help me with out a slip Now I want my money back so they can take their shorts so exactly what am I going to do with them if they don't fit my kids What kind of customer service is that if you be refunded your money just because of a lousy slip and there other whole of evidence