Human free will, I think, is limited to things temporal. We can choose to sleep in or wake up early, wear a button down shirt or pullover, eat this but not that, vacation here and not there, befriend him but not her, etc. However, because we are spiritually dead in trespasses and sins, we are unable on our own to respond to God's offer of grace; we must be prompted. When we hear the Lord calling and hear HIS offer, we either say "yes" or "no", but it is the power of the Spirit of God that quickens us to the point where we do say "yes." Is it irresistible grace? Or is it free angency of human beings that lifts us to the point of saying "Yes, I will exercise my free will and accept your offer, Lord."
Monergism vs synergism. All the debates throughout history have not settled the matter, excpet in the minds of those staunch proponents of either of the two positions.