I think it was well answered by test01. You cannot complete your Iman unless you accept All Prophets sent by Allah.
I have no authority calling anyone Non-Muslims.
Just an interesting clip which you might find interesting.
In 1953 Ulema sat to define what is Muslim? **And 22 Ulemas sat for few days but they could not agree on the definition of Muslim. **
Please Ignore the Video Heading as this does not define the discussion within.