The child Samuel ministered to Yahweh before Eli. The word of Yahweh was precious in those days; there was no frequent vision.
The other objection regarding the alleged "two accounts" of the prophecy regarding Eli is also of no significance.  G. B. Caird admitted that if  1 Samuel 3:12 refers to  1 Samuel 2:27-36 (to which it most certainly does refer) then "Both passages would be vindicated against the charge of lateness."[4]  Of course, he denied that any such thing should be admitted, declaring that, "Here Eli is warned of a disaster immediately impending ... and in the other passage  (1 Samuel 2:27ff) he is warned of a disaster spread over centuries."[5]