Poor customer service

Woolworths is my absolute favourite store for everything. I recently received gifts at my baby shower from friends. Some of the items I received 2 of and some items I thought I'd prefer in smaller sizes. So decided to exchange. Went to woolies at cresta and walked in with a bag security saw but just sanitized me. Anyway I've exchanged items before so know the drill, went to get the exact same baby growers just a few sizes smaller and proceeded to the till. As mentioned I received items I exchanged as gifts and did not have slips but all price tags were still on. Never worn because I'm still pregnant. I then gave cashier items and told her I have an exchange I dont want a refund I just want to swop sizes. I had 2 baby growers both 6-12 months and 2 short sleeve growers also 6-12 month that I wanted to exchange for newborn sizes I added a pair of socks too. Problem is cashier treated me like dirt! She asked if the security had checked my bag I said no. (I always say it's not what you say it's how you say it) Her tone may have suggested that I was not being truthful. Her supervisor was right next to her while all this was happening. 1 grower had a price tag on for R99 and she took the price off and rung it up at R109 I only checked my slip when I got home as I just wanted to get out of store because of her terrible attitude and could see that she just didnt want to help me. The other 2 growers had price tags on them and were marked down because of sale she says I'm giving you R21 refund not full amount ( again her tone) not are you aware these items are marked down etc.. so I had today in a balance of R26 odd rand ( now 26 is no problem to me) but her tone and the way she treated me as the customer and I was very patient with her. I'm really upset that she overcharged me on the 1 baby grower. It was just an awful experience at woolies and I wouldnt recommend anyone shop at the cresta branch as supervisor was right there and seemed on with the way cashier treated us. Which is shocking for woolies staff!