Pick n Pay - Bad service

I went to Pick 'n Pay Liquor-shop in Worcester (Russell Street). I took along my full complete case of 12 x 660ml Castle Lite empty bottles in a red case. I went into the shop to purchase a full case of 12 x 660ml Castle Lite beers. However, inside the shop they did not have an empty red case but they had more than enough Castle Lites in the fridges. Hence, i emptied my red case i brought along with.
At the till, i was accosted by a very rude and unpleasant security guard who accused me of trying to steal Pick n Pay's red empty case. I explained to both the cashier and security guard that, there is no empty red case in store hence the cashier is going to buy my empty red case complete with the 12 empty bottles to add it to her inventory. Then she will resell the complete full case to myself as usual. However, the security became very verbally abusive so, i just kept quite and paid for my own red case and left the shop. In most instances when i bring along my own complete empty case i am credited with R23,50 and i am billed for a complete case of Castle Lite case+deposit which comes to R211,22 which comes to a total of R187,72 minus my credited amount. Yesterday this total came to R199,22; hence i paid an extra amount of R11,50 therefore i re-bought my own red empty case.