Some people who call themselves Christians although they do not follow the teaching of Christ, makes a claim of other religions not being Christians. They make the statement about JWs. They are the only group that go house to house preaching the good news about God's kingdom.
Luke 8:1 8 Shortly afterward he traveled from city to city and from village to village, preaching and declaring the good news of the Kingdom of God.+ And the Twelve were with him,
14 And this good news of the Kingdom will be preached in all the inhabited earth for a witness to all the nations,+ and then the end will come.
Matthew 28:19, 20
19 Go, therefore, and make disciples of people of all the nations,+ baptizing them+ in the name of the Father and of the Son and of the holy spirit, 20 teaching them to observe all the things I have commanded you.+ And look! I am with you all the days until the conclusion of the system of things.”*
Acts 20:20 while I did not hold back from telling you any of the things that were profitable* nor from teaching you publicly+ and from house to house.+
Those who do this are true Christians.