Policy rules not transparent and to to shove it when raising the issue

I have had the worst service at Truworths Savannah Mall polokwane. I returned a sale item, and was informed that I could not exchange for the same price, and was told to take the money and they were not willing to even assist me. I requested head office be called, and the lady from head office hung up on me. The lady who assisted me was so rude and told me to take the money and walk. I asked they show me on the slip the policy that speaks to this exchange and was told it's not there and it was something that the system just knows and is not written anywhere. I am livid