Manager denying me to purchase

I went to buy 50 Coca Cola 2L drinks and the manager denied me saying he wont have a stock for the following day if i purchase the drinks. I tried to find the sense and the logic behind this and he couldnt clarify me. Big shop like pick n Pay cant allow an individual to purchase items that are within the shop. I still dont understand this manager by the name of Jean at Sanridge Pick n Pay. I ended not buying because he said he is not gorverned by any pick n pay policy but he has his own established policy.