God calls them to Heaven, but they can still say no. C.S. Lewis addresses this problem by pointing to Philippians 2:12-13:
“So then, my dear friends, just as you have always obeyed, not only in my presence but even more in my absence, continue working out your salvation with awe and reverence, for the one bringing forth in you both the desire and the effort – for the sake of his good pleasure – is God.”
By our free will, we are complying with God’s plan. Without God, we wouldn’t be able to do any of those things. The Church’s teaching, to my understanding, is that free will is only possible through the Will of God (that God wills us to have free will, because it is *inherently *good… even if we do bad things with that will).
Predestination recognizes that God has the ultimate power and authority. He could stamp out sin with a snap of the fingers, but in the process, He’d be squelching out a lot of us who just need more time (Matthew 13:24-30, 36-42). So God lets us have free will, which is to say, He lets sin exist, b/c our being able to freely love Him, and work our way back to Him, matters **that **much. So in that sense, the presence of sin in the world isn’t a reflection of weakness in God, but rather, of His love.
But He goes beyond that. He doesn’t just let us work our way back to Him. He stands at the door and knocks (Rev 3:20-22). Even then, we could not open the door. But why on Earth would we? Sin and temptation, I suppose. Shutting God out inadvertantly. Eegh.