Even when I know & the servicing dept admit to a screw up, I never rant & rave on like a pork chop because ultimately they're the ones doing the work & so it's always best to extend to them respect & politeness & in return they will do same & then some. And so it becomes a good long term relationship.
I have had some major shit go wrong with new cars in the past where Tech Div have had big input, after a little while I was in constant & direct contact with them trying to sort out issues and being diplomatic & polite meant that they were always willing to help & treated me with great respect. In my experience Toyota are a great motor company with great people who care.
I can't say that for other car companies though !