OLD Tyres on New Vehicles

Purchased a New Tiguan from Bryanston Hatfield 2019 and vehicle was fitted with tyres manufactured in 2017. With less than 40 000kms on the tyre, the tread is still good but the sidewalls have cracked due to age "not mileage" and has had to be replaced. After months of back and forth between Hatfield and VWSA blaming each other for fitting old tyres they eventually came back to me and told me to deal with it... Was then reported to Ombud who came back to us and told us its normal wear and tear even though we explained that the tread is good but tyre side walls are cracked due to age. We still have the tyres as proof but once again the customer is wrong. I will continue to cause reputational damage to vwsa by getting friends and family to post this on social media because obviously their reputation is worth less than them admitting to their error