Bad attitude and wrong pricing

I went to Mr price home in sunnypark Pretoria yesterday. I was buying cushions, when I was done paying the one was marked down to R100 and the other one was not marked down but is the same item same code number, I asked how come the same item but different price and the guy by the name Walter told me is because the other one is old stock, I said but doesn't make sense because is exactly the samething, he later agree that they make a mistake and they will rectify it. I told him that as a customer he have to give me both with the marked down price and he refused, I asked to see a manager he said he's not around but he will come tomorrow meaning today (17/03/2018), I said is fine give me my money I will come tomorrow so that I can talk to the manager maybe the manager will explain better than you, the other lady said to me Walter he's the store manager, I said I will call head office because you Walter as a manager you are not explaining better so that I can understand. And Walter get angry I don't why because I was not shouting or he get angry because he feel threatened by me saying I will call head office. I told him there's no need to get angry because am not going to call head office to talk bad about him I want know how come same items on the shelves but different price. Things get out off hand he end up clapped me on my face, it was my first time to be beaten like that in my life, more especially by a store manager, he supposed to act like a manager. I don't know how he became a manager in the first place. Am so angry as I speak now. I went to police station to open a case of assault, they said I should come back today because the store is already closed so that they can view the camera and see what happened. Peter can you please help me as a customer because the way the store manager treated me it was bad, he even told me he don't care about my rights as a customer and in his store fact that customer is always right it doesn't work he also told me that I can go wherever I want he won't get fired. Please Peter help me.