New Policy (Customer Services)

Today i went to Shoprite at Goldspot (Vosloorus) to exchange low fat milk for full cream, that i had bought at different Shoprite (Goldenwalk (Germiston), and the Manager told me about the new policy, whereby you are not allowed to exchange item you bought at (Goldenwalk), now what makes me angry is that the fact, the item to be exchanged is a Shoprite Brand. So for consumers this policy i feel is UNFAIR, kindly address.