Is the phrase "I will have you know that" incorrect?
It's causative, something like the explanation that I am about to give you will make you think otherwise. It's often used to correct someone's erroneous assumptions. For example, Coworker1: You called in sick yesterday, huh?Did you have an enjoyable "paid" day-off? Coworker2: I will have you know that it wasn't "enjoyable", that I was indeed home in bed with a fever.