Unreliable car and poor customer service

I’m very frustrated , I took my Nissan magnite to the dealer on the 6th of September 2023. It had an engine problem which showed anti pollution signs on the dash board. I have laid a complaint with Nissan SA , at the beginning of December they said they have changed the whole entire engine because they couldn’t fix it, now they said they are waiting for police clearance certificate which they don’t know for how long ( mind you this process takes about 2 days) and I have been waiting for weeks now. They don’t call unless you call to update you. The Nissan SA customer service lack’s problem solving skills. No solution from them at all.now i dont want this car , i just want them to cancel the deal because the car was less than 8 months when the problem started and i dont even believe that they changed the engine Someone please help me, I’m just a single black woman whom is not taken seriously by the dealership. Anyone who can assist me please