The tetragrammaton does not appear in the Kingdom Interlinear the word for word translation of the Cchristian Greek Scriptures published by the WTB&TS
Therefore the name Jehovah should not appear in the New Testament (NWT)
In the same publication at John 1:1 the word for word translation says," In the beginning was the word and the word was with God and the word was God"
As you point out their are heaps of scriptures of Christians witnessing to ,for,or about Jesus Christ..( approx.30 ?)
Their is not one that I know of that says Christians are to be witnesses of Jehovah.,not one.