"Called" in Romans

I am reading through Romans 1-3 every day for the month of August, and I noticed how Romans 1 describes our salvation as an act initiated by God:

• 1:1 - "Paul, ... called to be an apostle"
• 1:6 - "you who are called to belong to Jesus Christ"
• 1:7 - "To all those ... called to be saints"

Why does Paul describe our salvation in terms of God's calling us? While it is completely true that we must answer the general gospel call to repent and believe the gospel, we must recognize the unbeliever's complete inability to do so without a "change of heart." Like Lazarus, an unbeliever cannot stir himself to life, or cry out for help, or say a prayer. Unless we are called by God out of our tombs, we cannot even cry out to God for rescue! Read the words to Amazing Grace again for the first time.