Terrible Kia Service

Took my vehicle for service at Kia Table View on the 26th June 2020, they serviced the vehicle and informed me that everything is well. Was driving the same day from Cape Town to Johannesburg until the vehicle decided to overheat at 3am on the 27th June 2020 140km away from Bloemfontein, towed the vehicle to Kia Bloemfontein for them to check it.The result was the radiator cap pressure.and its a service related issue which was supposed to be picked up. Now doesnt wanna be liable for the matter and refereed me to Motor Ombudsmen