No return on say

I am very disappointment with your store in nkomo village mall. I was there earlier for exchange but unfortunately I couldn't find the size and I had to return. But because the item was on sale I was told I cannot return but exchange and it was never stated on the slip. Of which I ddnt have a problem but the attitude of the manager... she was even telling that I should stand there for as long as I want, no one will help me. I called your head office I was directed to the area manager I think. But he was not on hearing what are my problem but instant he told me to give out my id copy and my bank statement. For what I don't know because I was not going to open an account. And by the look of things, everyone that i tell about their service, people are not surprised because apparently that's how the manager speaks