in the insights u said that yitzchaks name was never changed since it was named by hashem but we know that hashem gives ruach hakodesh to name a child
FROM INSIGHTS TO BERACHOS 13:
(a) RAV NISIM GA'ON quotes the Yerushalmi (Berachos, end of ch. 1) which points out that Avraham's original name was given to him by his father, Terach. Yakov's name was given to him by his father, Yitzchak. Yitzchak's name, though, was given to him directly by Hash-m Himself (Bereishis 17:19). Therefore, there was no need to change it.
Binyamin , brooklyn
The Yerushalmi does indeed say that Yitzchak was one of four people named by Hash-m, and therefore his name was not changed. This is because when Hash-m makes a statement that this is what someone's name should be called, He takes into consideration everything that will happen to that person in his lifetime. However, even if a person has Ruach Ha'Kodesh (which is far less of a level of Heavenly assistance than Hash-m's direct naming) when naming a child, it is possible that this will only assist him as far as naming the child with a name appropriate for him in the beginning of his life. It is not a guarantee that there will never be a time in his life where he will not benefit from a name change.
(Of course, this is assuming the person is a Tzadik, as was Yitzchak when he named Yaakov. Someone who names after evildoers etc. is obviously not meriting of Divine assistance in choosing such a name.)
All the best,
Yaakov Montrose