So God Doesn't Change His Mind?

In Numbers, King Balak of Moab begs Balaam, a man known for his curses on people, to come curse the Israelites because he is afraid of them entering his land. Balaam, being faithful to the Lord, tells Balak that he can only say what the Lord allows him to say. So when Balaam blesses Israel instead of cursing them, Balak is outraged; he tells Balaam to take the blessing back. This is Balaam's response: 

   "He is not human, so he does not change his mind. 

Has he ever promised and not carried it through?" 23:19

While the Bible may have had a different story if God had cursed Israel here, but I don't know if what Balaam is saying is true. How many times did God promise to wipe out the Israelites because of either their idol worship or their constant complaining but Moses (sometimes with the help of Aaron) change God's mind? Over and over throughout Exodus and Numbers. If Moses wrote these books, how can there be such a discrepancy in God's character? Call me anal, but I like consistency. Inconsistencies make me question the whole thing, which is it- this or that? I'm not ready to throw the baby out with the bathwater just yet, but come on, help me out here, Moses.

Here's what I wrote a few weeks ago on the same thing: Does God Change His Mind?