How can one be "Called to preach" if they don't "hear?"
The Lord Jesus Christ said, "He that has ears let him hear?" Apparently some do not hear?
Yes the Scriptures are "cannoned" but who put the cannon together?
"All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work," is not a verse to indicate that the cannon of 66 books is all that God will ever say on any subject concerning humankind. The verse just can't be used that way. The verse is stating that the Scriptures are "profitable, useful, a tool" but in no way is the verse exclusive.
It would be difficult to sit under a pastor who has not walked intimately with God and heard directly from God, seeks out the wisdom and direction of God, and is given direct insight by God.
Not saying that the typical charismatic thinking is correct, nor is much of anything in that camp to be emulated, or assumed as normally Scriptural.
Just encouraging the readers to trust that God does directly hear and answer the prayers of those He calls His, and that He speaks to the heart and living of every believer, if they are listening.
But remember that, like Moses standing on Holy ground, the Creator doesn't tolerate fools. Come humbly, come earnestly, come honestly, come in worship with an open heart and Bible, and don't be in a hurry. David waited three days, the Lord Jesus Christ would spend hours in prayer. Often the believer who is too busy with the fleshly, will only reap what is fleshly.