The trouble is a person CAN'T hear the call unless God grants them understanding.
Luk 8:10 And He said, "To you it has been granted to know the mysteries of the kingdom of God, but to the rest it is in parables, so that SEEING THEY MAY NOT SEE, AND HEARING THEY MAY NOT UNDERSTAND.
The ability to believe the Gospel -- that is, deposit of faith -- is given everyone, or Christ would not be calling us to have childlike faith. The distinction with the parables is temporal, preceding the Resurrection and the Great Commission, according to which the entire gospel is to be preached to "all creation". The church is sent to overcome the limited ability of some to understand the scripture; such understanding, however, cannot be equated with faith.
I find it, however, remarkable that you acknowledge that the call is to all. Is it the standard Calvinist teaching? How does it square with the notion that God does not want all to be saved?