For those who believe in an omniscient God, as all believers must, how can you assert free will?

An omniscient being who knows all, and who has a, “plan”, cannot allow free will; as an expression of free will would negate omniscience.

Ergo, an omniscient being knows, knows, what my next action, no matter how incidental, or small that action may be, is. I cannot therefore act in anyway other than in accord with that omniscient knowledge. Consequently I have no free will.

If I can exercise free will, then God is not omniscient, for I will have acted outside of his preordained knowledge.