Poor service

I bought 2nd hand KIA Sportage 2019 with 24000km at KIA Springs. 32000km my engine light came on. Took the car in they found the throttle body plug came loose and they fix it. On collection of the vehicle they asked if someone worked on the car??? Really??? My service plan and warranty is still in place why will I go pay someone to work on the vehicle if I can do it for free. 2ndly after collecting the car 8days and less then 300km later it came back on again. Now they switched it off and said I should monitor it. They don’t no wots wrong.