Mr Price Return Policy

We bought a pair of sneakers from Mr Price Sports Horizon View in October'20. After wearing them on a few occasions, the 1 sneaker started hurting my husband over the breach of his foot due to a piece of the metal that covers the shoe lace hole, pertruding into his foot. The stitching on the side of the shoe also started coming apart. We visited the Horizon View branch end Jan'21 to exchange for a new pair. The branch manager informed us that it would not be possible due to the store's own Return Policy (30 days). How is it possible that a retailer's policy could overrule the CPA (6 months)?