Our Gemara on Amud Beis discusses the use of the Hebrew word “es”, which has no English translation, but signals an association between a significant object, and other less significant objects that are subsumed within the context. Thus, Rabbi Akiva famously derives from “Es Hashem Elokecha Tira” “Es Hashem your God you must fear” (Devarim 6:13), to include fear for Torah sages under the directive to fear God. That is, a less-significant related item, included within the object of focus. Or in a more profane example, “es besaro - es its flesh” (Shemos 21:28) teaches that one cannot benefit even from the skin of the stoned ox. That is, the skin is a secondary, less significant object included in the directive forbidding the stoned animal’s flesh.
Sefer Daf al Daf quotes the Hagahos of Rav Katzenellebogen (Berachos 13a) who uses this same idea about the word “es” to explain the difference between the changing of Avaraham’s name and Yitschok’s name.
By Avraham, it states (Bereishis 17:5):
No longer shall your name be called Avram, but your name shall be Avraham, for the father of a multitude of nations I have appointed you
By Yaakov, there are two separate verses, one where the angel renames Yaakov, and followed by God’s confirmation.
(Bereishis 32:39) states:
He [the angel] said, No longer will your name be spoken of as Yaakov, but as Yisrael, for you have contended with God[ly beings] and with men, and you have won.
And (ibid, 35:10):
[Hashem says,] Your name is Jacob, You shall be called Jacob no more, But Israel shall be your name.” Thus he was named Israel.
Gemara Berachos (13a) notes a distinction between Avraham and Yaakov:
תָּנֵי בַּר קַפָּרָא: כָּל הַקּוֹרֵא לְאַבְרָהָם ״אַבְרָם״ — עוֹבֵר בַּעֲשֵׂה. שֶׁנֶּאֱמַר: ״וְהָיָה שִׁמְךָ אַבְרָהָם״. רַבִּי אֱלִיעֶזֶר אוֹמֵר: עוֹבֵר בְּלָאו, שֶׁנֶּאֱמַר: ״וְלֹא יִקָּרֵא עוֹד [אֶת] שִׁמְךָ אַבְרָם״.
Also, with regard to Abraham’s name, bar Kappara taught: Anyone who calls Abraham Avram transgresses a positive commandment, as it is stated: “And your name will be Abraham” (Genesis 17:5). This is a positive mitzvah to refer to him as Abraham. Rabbi Eliezer says: One who calls Abraham Abram transgresses a positive commandment, as it is stated: “And your name shall no longer be called Abram, and your name will be Abraham, for I have made you the father of a multitude of nations” (Genesis 17:5).
אֶלָּא מֵעַתָּה הַקּוֹרֵא לְיַעֲקֹב ״יַעֲקֹב״ הָכִי נָמֵי?!
The Gemara asks: But if that is so, one who calls Jacob Jacob, about whom it is written: “Your name shall no longer be Jacob, but Israel” (Genesis 32:29), also transgresses? (Yet we know this not to be the case!)
שָׁאנֵי הָתָם דַּהֲדַר אַהְדְּרֵיהּ קְרָא, דִּכְתִיב: ״וַיֹּאמֶר אֱלֹהִים לְיִשְׂרָאֵל בְּמַרְאוֹת הַלַּיְלָה וַיֹּאמֶר יַעֲקֹב יַעֲקֹב״.
The Gemara answers: It is different there, as the verse reverts back, and God Himself refers to Jacob as Jacob, as it is written before his descent to Egypt: “And God said to Israel in the visions of the night, and said, Jacob, Jacob, and he said, ‘Here I am’” (Genesis 46:2).
Rav Katzenellenbogen says this is why by Avraham the verse above uses “es” in regard to the name of Avram, to connote that even as a secondary name Avram will no longer be used, unlike with Yaakov.
This explains the what, but not the why. Why is Avraham’s name change permanent, but Yaakov’s name variable? Reflecting on the context, Avraham was the first Jew in a sense of devoting himself to the lost practices of monotheism, and being assured that his children were part of a special covenant. He was, effectively, a Ger. As our sages taught, “A Convert is like a newborn child” (Yevamos 62a). The implication is that a convert goes through a process of fully breaking from the past. This is what Avraham did. On the other hand, Yaakov’s name change represented an additional dimension to his life, effectively beginning the peoplehood of Israel. As such, he can alternate between personal and public destiny.
These two different paradigms of change and destiny are important to consider. Sometimes we reach a new level which necessitates a clean break from the past. Other times, we reach a new level that has application in one dimension of self, but integrates or alternates with other valid aspects.
Translations Courtesy of Sefaria, except when, sometimes, I disagree with the translation 
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