Here is an exchange of where our Lord Jesus irresistibly calls one but not another. I love this portion of scripture (the whole thing is too lengthy to post here) for it is chock full of God's salvation.
Joh 9:36 He answered, "Who is He, Lord, that I may believe in Him?"
Joh 9:37 Jesus said to him, "You have both seen Him, and He is the one who is talking with you."
Joh 9:38 And he said, "Lord, I believe." And he worshiped Him.
Joh 9:39 And Jesus said, "For judgment I came into this world, so that those who do not see may see, and that those who see may become blind."
Joh 9:40 Those of the Pharisees who were with Him heard these things and said to Him, "We are not blind too, are we?"
Joh 9:41 Jesus said to them, "If you were blind, you would have no sin; but since you say, 'We see,' your sin remains.
Nowhere does that suggest that Jesus meant FUTURE sins, as well. Otherwise, WHY did Christ give the Apostles the ministry of forgiveness of sins AFTER THE RESURRECTION??? There is nothing in the Scripture that suggests that a person could not fall away. Remember, all of the letters of the Scripture were addressed to OTHER CHRISTIANS. And over and over, the writers warn them to persevere, to beware not to fall away, to not be tepid in their faith.
Please note while our Lord Jesus opened this man's eyes, he didn't understand who the Messiah was until Christ revealed Himself to him. Where is the "universal call" that we hear everyone telling us about? The Lord doesn't do the same for the Pharisee and specifically states their "sin remains".
Jesus over and over called to the Pharisees! Jesus noted it was THEIR BLINDNESS, their stubborn hearst, not Christ's lack of calling that kept them in the dark. They REFUSED to believe that Jesus was offering something that was outside of their little box they built for God.
Regards