Bad service and expiry date on goods.

I purchased a 6 pack of yogurts about a week ago from Woolworths. Yesterday I took two with me to work to find that one had mould. Took my complain to Woolworths in Brigh****er Commons. Mahlatse Matlakala who is supposedly the manager in the food section who was very unhelpful. Princess Mathejane was the supporter of Mahlatse's behaviour treating me as if I went to ask for free yogurt asking me if I kept the yoghurt in the fridge. Really? Natasha Sithole who is the store manager, was unavailable. The only person who was willing to assist was Xolani Simelani. By the time he came to my aid, the damage was already done by Mahlatse telling Princess that I should go away and to stop stressing him. I commend Xolani for trying to help in this regard. Princess was rather protective of her partner when I inquired about what was said as I walked away. My annoyance is more on the services that I received over goods that are in such condition. To be told about the sell-by date, when the use-by date is not reached and Woolworths policies which do not make sense to me as a customer put me off completely. What happened to consumer rights and customer service?