I did not see CB's post above. Like probably everybody else I haven't had time to read every one, particularily when not directed to me.
However, in regards to CB's point, every person who does not accept God's call bears their blame. They are without excuse because even though they knew God they did not honor him as God. But every Christian who accepts God's call does so because God opened His eyes and ears to hear the truth.
Both hear but only believers hear and understand. It's no different than God sending plague after plague and still Pharoah could not understand.
I doubt anyone here disagrees with that. But thats a long way from stating that no one who is called cannot resist.