I bought a car and the engine died within 24 hours

I bought an ML 500 on the 13th of October at we buy cars midstream and within 24 hours the car broke down, and I was told buy the mechanic that the engine seizes, and then I immediately submitted my complaint to we buy cars on their website, but I never got a response. I was hurt that just after buying a car within 24 hours it died and you can't get assistance from the dealership. I even tried to call their call center but no reply.