God's call to salvation in the New Testament is to believe on our Lord Jesus Christ (Acts 16:31). Those who respond to the call of God are saved. God calls us out of darkness into the light of Jesus Christ (1 Peter 2:9). God calls us to faith in Christ by the word and the Spirit.
God calls us to believe the gospel of Jesus Christ. We do so through repentance toward God and faith in our Lord Jesus Christ (Acts 20:21). The gospel is for whoever, but not all will respond (Romans 10:13). Those who do are called according to God's purpose (Romans 8:28-30).
God calls us out of spiritual darkness into the light of Christ. Our eyes of understanding are open to Christ crucified for our sins and raised from the dead for your justification. By God's grace, we are able to live in the light. "But if we walk in the light as He is in the light, we have fellowship one with another, and the blood of Jesus Christ His Son cleanses us from all sin" (1 John 1:7).
God calls us by the power of the Holy Spirit to believe the word of the gospel (Romans 1:16). God calls us to respond by turning to God through faith in the Lord Jesus Christ. Our hearts are changed by the grace of God. Certainly, the gospel is preached to all, but God's call is only effective in those who repent, or turn to God, through faith in Christ.