warranty

In 2019 I bought a Opel Crossland X demo at Williams Hunt Centurion (was registered in my name 2019) on the 28th of January 2020 I took the car in for them to check why my car does not start which they told me it’s the battery which should have a 24 month warranty as per Opel’s booklet but according to them this wasn’t the correct battery and was not there problem to replace it. So my question is why was this battery in the car when it was sold to me, why does Opel sell cars without original parts? I want Opel SA to trace who replaced this battery and I request to be fully covered or paid back by Opel!