How do we know God's calls to us are effectual?

The sermon illustrates that God's calls, specifically in the story of Samuel, are effectual and inevitable for those whom He has chosen. In 1 Samuel 3, God called Samuel multiple times until he recognized the voice of the Lord. This shows that while God's general call can be ignored, His specific, effectual call will ultimately succeed in bringing His elect to Himself. As stated in John 10:27, 'My sheep hear my voice,' confirming that those whom God has chosen will respond to His call, demonstrating His sovereign grace in salvation and His power to draw sinners to Himself.