failure to replace damaged goods

My husband purchased a ring and earing set from Stearns in pine crest mall pinetown on the 21st December @ 13.21 pm . When opening the gift we then noticed that the stone was loose as one of the pins were damaged. The ring was wrapped in store when purchased and was not opened until then. My husband returned to the store on the 29th where the ring was checked and it was established that it was damaged . My husband was told that he could either get a voucher for the value of the ring or they could replace the ring with stock they had sourced from another store . He opted to have the ring replaced . We received a call on the 31st to say we could pick up the new ring to which , my husband advised that he could only come through the following week which he was told was fine , yesterday he returns to the store for the 3rd time and is now told that he needs to pay in extra as the ring is no longer on promotion . This is unacceptable as at no point was he told on the 29 th that he would need to pay extra and why should we have to pay more when we were sold a defective item . Had we not been sold a broken item we would have paid the promotion amount . Please look into this urgently