Since the time that the Quran was revealed, people who resisted its message wanted to change it. This Quranic verse (see video below) clearly provides an answer to those people through Prophet Muhammad (peace and blessings of Allah be Upon Him).
“And when Our verses are recited to them as clear evidences, those who do not expect the meeting with Us say, “Bring us a Qur’an other than this or change it.” Say, [O Muhammad], “It is not for me to change it on my own accord. I only follow what is revealed to me. Indeed I fear, if I should disobey my Lord, the punishment of a tremendous Day.” Quran (Surah Younus:15)