Flat Aquelle Sparkling Water Purchased at Checkers

We purchased 2x packs of 500ml of Aquelle Sparkling Water from Checkers, however upon opening it, the water was completely flat and not sparkling at all.

This is disappointing as the product was sold and priced as sparkling water, yet did not meet basic quality expectations. I specifically bought it for the carbonation, which was nonexistent.

Please advise on how this matter can be resolved, either through a refund or replacement, and what steps will be taken to ensure better quality control going forward