Cell C shop refuse to replace the screen guard under guarantee

I bought a BodyGlove Tempered Glass Screenguard for R399 on the 09October 2020 and was told that I have a 12 months warranty in cass of a damage .On the 4th December 2020 ,I went to the shop and was told that it cannot be replaced as it had cracked...What does the warranty entails...I was told that it's going to be the shop loss as the supplier will not take it back as it was cracked. I need the screenguard to be replaced