Not following the refund policy - staff have attitude and bad customer service

Bought a gown in Ackermans last weekend on promotion and this weekend went to exchange it due to wrong size same item and the cashier Andrea Zas told me I have to pay a normal price and when I ask why because it's same item am exchange she couldn't example and the manager (Kaylyn Sors) when she came to override she had an attitude she didn't example why I had to pay the normal price am still confused....Ackermans in Somerset West worse I have been in to staff have attitude, bad customer service....