Green Dot Cars sold me a defective car

I am very disappointed with the terrible after service. We bought a Volvo XC60 end of December 2018. We did at the time receive a good service, we even referred all our family and friends resulting in 6 cars been bought from Green Dot Cars. 7 months later, the cars packs up and piston apparently cracks. As I bought the car and warrantee from Green Dot Cars, I contacted them to let them know. Not worrying too much, as I had peace of mind that I had the warrantee, I was advised by the mechanic, That I missed a service, now they won't pay. looking back, although i did sign, I was not advised properly about the service moving forward. A car does simply not break down. was advised that it was an engine defect. Green Dot Cars are offering no way of helping me in this situation. We feel let down and feel they have sold us a defective car.