Ford sold my dad a car that was not 100% road worthy

My dad bought a used Mazda BT50 in November last year and in July already giving gearbox problems. I contacted the sales guy and emailed him the report and no response from him. Very disappointing for a big company. I dad was admitted in hospital due to the stress of knowing what's wrong with his car when he hasn't even driven it for a year. We almost lost my dad because of the not road worthy car sold by Ford.