The verse you brought up mentioned the Jews and Christians. The answer was, the Jews rejected Muhammad pbuh for not being a Jew and claiming they had corrupted the Torah. The Christians too denied him for claiming Jesus pbuh was a Prophet of God, and wasn't killed or crucified. For this reason these two groups turned their back on God even though both Deut 18:18, Isaiah 42 and the words of Jesus pbuh in the NT made clear he would be a non Jewish Prophet, who they must listen to or be amongst the losers. This is theology, which I think doesn't interest you, but anyway, I'm trying to give context to the verse you cited.
Muslim-UK said, "This is theology..."
And theology is fiction. To me you believe in a belief system that has no reality. Is there some reason that you are not a Jain or a Shinto? Perhaps you were born and raised a Muslim, and weren't raised to believe in Buddha or Shiva.