Avram's name was changed to Avraham; Ya'akov's name was changed to Yisra'el. Yitzchak's name was not changed.
In the case of Ya'akov, we see that his name was changed in association with a specific event, namely, defeating the angel. Avraham's name change does not appear to associated with a specific event - at least not from the location of the name change in the verse or nearby surrounding verses where the change is mentioned.
What events or specific qualities merited Avraham and Ya'akov to warrant a name change, yet no such change was deemed necessary for Yitchak?