It should be really easy to see that being called a friend has to do with understanding, and being called a servant has to do with not understanding.

Abraham's test was the most severe that could come to a human being. Had he failed under it, he would never have been registered as the father of the faithful. Had he deviated from God's command, the world would have lost an inspiring example of unquestioning faith and obedience. {1BC 1094.4}

Abraham's unquestioning obedience was one of the most striking instances of faith and reliance upon God to be found in the Sacred Record. . . . Just such faith and confidence as Abraham had the messengers of God need today. {AG 133.6} We cannot overestimate the value of simple faith and unquestioning obedience. It is by following in the path of obedience in simple faith that the character obtains perfection. {LHU 139.6} When we are in right relation to God, we shall recognize Christ's authority to direct us and His claim to our unquestioning obedience. {2MCP 782.4}

"By faith Abraham, when he was called to go out into a place which he should after receive for an inheritance, obeyed; and he went out, not knowing whither he went." Hebrews 11:8. Abraham's unquestioning obedience is one of the most striking evidences of faith to be found in all the Bible. To him, faith was "the substance of things hoped for, the evidence of things not seen." Verse 1. Relying upon the divine promise, without the least outward assurance of its fulfillment, he abandoned home and kindred and native land, and went forth, he knew not whither, to follow where God should lead. "By faith he became a sojourner in the land of promise, as in a land not his own, dwelling in tents, with Isaac and Jacob, the heirs with him of the same promise." Hebrews 11:9, R.V. {PP 126.2}

In a vision of the night the divine Voice was again heard. "Fear not, Abram," were the words of the Prince of princes; "I am thy shield, and thy exceeding great reward." But his mind was so oppressed by forebodings that he could not now grasp the promise with unquestioning confidence as heretofore. He prayed for some tangible evidence that it would be fulfilled. And how was the covenant promise to be realized, while the gift of a son was withheld? "What wilt thou give me," he said, "seeing I go childless?" "And, lo, one born in my house is mine heir." He proposed to make his trusty servant Eliezer his son by adoption, and the inheritor of his possessions. But he was assured that a child of his own was to be his heir. Then he was led outside his tent, and told to look up to the unnumbered stars glittering in the heavens; and as he did so, the words were spoken, "So shall thy seed be." "Abraham believed God, and it was counted unto him for righteousness." Romans 4:3. {PP 136.3}

So I dont think that because sometimes we question something ... it necessarily means we arent God's friend or even that we dont have faith. I think God understands.

15: Henceforth I call you not servants; for the servant knoweth not what his lord doeth: but I have called you friends; for all things that I have heard of my Father I have made known unto you.(John 15)

The point is - It is possible to obey Jesus before understanding His reasons for giving the command. Such obedience is not slavish.