The problem with some is that when they look at Romans 8:28-29, they see something that's not there and consciously or unconsciously, they read that something into the text. Here's Romans 8:28-29: "And we know that God causes all things to work together for good to those who love God, to those who are called according to His purpose. 29 For those whom He foreknew, He also predestined to become conformed to the image of His Son, so that He would be the firstborn among many brethren."
Upon reading the word, "called," we see that in this text, Paul does not inform the reader concerning how God calls them, also He doesn't say that God only called them. He explains how God calls by the the gospel in other texts: II Thessalonians 2:14; Galatians 1:6-7; Romans 1:15-16; 10:17. To say that this "call" is irresistible or that there are two types of calling is to see what's not there in the text.
Who are the ones Paul is talking about: "those who love God"? What are they per-appointed to? "To be conformed to the image of Christ." To say that they were pre-appointed to salvation is to see something that's not in the text. The two, loving God and salvation are not the same. Those who respond positively to "the call" of the gospel are per-appointed "to be conformed to the image of Christ."
When will the ones who responded to the call be conformed to the image of Christ? Not in this life but when they are resurrected from the dead. Jesus is said to be the firstborn through His resurrection (vs. 30). The reader is in a resurrection context, an eternal security context. God's calling and pre-appointment all depend, according to vs. 28, on whether a man loves God, not on some decisions made in eternity past as to what few go to heaven and the majority of those who have ever lived go to hell, all decided before they were ever born, according to the philosophical system of Calvinism. To say that this text is saying that is to see what's not there
God's foreknowledge is not an act of God; God's foreknowledge is an attribute of God. One should also notice that regeneration is not in the list given in the verses.
Once a person responds positively to the gospel God pre-appoints him to be conformed to the image of Christ at the resurrection. as I John 3:2 promises, "Beloved, now we are children of God, and it has not appeared as yet what we will be. We know that when He appears, we will be like Him, because we will see Him just as He is.