Bad customer service

Worst experience ever at the n1 city Mr price on the 27 October 2018 at about 1-2 o clock. I'm a regular customer as I used to work in the mall (in retail) and live close by. Never had this experience before! I bought some items for my daughter and wanted to exchange it the same day for a bigger size because when I got to the car and fit it on it was too small. I had the slip and all the tags were on. When I got to security she asked me to write my name on a sticker (rudely) so I did anyway. I took the items out the bag as I had alot of other items and personal belongings in the bag she shouted me as if I was stupid asking me why I'm taking the items out I was so embarrassed as there were people around and obviously looking. I told her I just want to exchange the two items in a firm voice as I was upset. The manager comes not knowing what's going on telling me it's store policy?? Almost like she knew what went on I told her to tell her security to speak nicer to the customers and she went on talking about store policy. I told her that I will never shop here again I'm a regular loyal customer and i will be laying a complaint and her reply was be my guest. I was really upset still am and I would like an apology from both the security and manager on duty this day. I know stores have policies I worked in retail myself I won't look for unnecessary drama as I know how tough it can be. my fiance was also present at the time of this happening