The Holy Spirit will overcome all rebellion and effectually call the Elect.
This doctrine does not teach that no one can resist the Holy Spirit - that would clearly contradict Acts 7:51 - but that no one can finally resist His sovereign call. It's God who brings us to faith and overcomes our Total Depravity. Due to the hardness of our hearts, none of us would choose Christ unless we were sovereignly called by God. The Bible teaches :
John 1:13 Born not of natural descent, nor of human decision or a husband's will, but born of God.
John 6:44 No one can come to me unless the Father who sent me draws him, and I will raise him up at the last day.
Acts 16:14 One of those listeners was a woman named Lydia... The Lord opened her heart to respond to Paul's message.