Very very Disappointed Customer

Our appointment did not go well with Nissan Gateway. The dealer principle Trevor Munsamy states that the alternator was replaced & the Nissan NP200 is as good as new. Cannot guarantee it will not break down tomorrow. Says that as per the CPA he is allowed to repair a brand new vehicle & give it back to us. He is not changing the vehicle as It is already registered on our name. Also his service manager states that I must be careful as they are a big company & I must be careful about what I post on social media. I am extremely disappointed and angered with the outcome. Brand new getting repaired??