I understand the differences between affect and effect, and generally when to use them. However, in some cases while reading I have seen authors use the phrase "effect a change" (among others) meaning, I think, to cause a change, or to bring about a change. Using "affect a change" seems wrong/awkward; so is this acceptable use?
You effect a change when you cause the change to occur. When you are the one to bring the change about.
You affect a change when you change the change. When the change is already there and you influence it.