They're "Church of Christ"

Misconceptions arise from various sources and are often difficult to eliminate. One such example is that of the common phrase used by so many when describing those who abide by the doctrine of Christ and are a part of His church.
I can’t tell you how many times I’ve heard people say, “Well I was raised (fill in denomination hear), but my spouse was raised ‘Church of Christ.” Or perhaps it goes something like, “She’s (fill in denomination here), but her husband is ‘Church of Christ.’”
Though many don’t know it, and perhaps they’re just not thinking about it, they are trivializing God’s divine institution when they use such conversation. It plants the church of our Lord into a denominational genre, and therefore applies to the church a social bond with other bodies of belief that are not of God.
Jesus came to build His church, and did so according to the eternal plan of God (Matt. 16:18; Eph. 1:22, 23). When we speak of the church of which we are a part, we recognize it as the one body Jesus bought with blood, established at Pentecost, still in existence today (Eph. 4:4-6; Acts 20:28). There is no universal title for the church outside of the Biblical titles to which we see it ascribed. God inspired men to call it by its proper name, as the church of Christ (Rom. 16:16), the church of the Firstborn (Heb. 12:23), the church of God (1 Cor. 1:2), or even just “the church” (Eph. 5:23).
But followers of Jesus are not “Church of Christ” or “Church of Christers.” When we say someone is “Church of Christ”, we go beyond the description allowed in the Bible for those who are in the church. We are to be called simply “Christians” (Acts 11:26; 1 Pet. 4:16), or “saints” (Rom. 1:7). A true Christian is one who is in the church and belongs to Christ, the One who is Head of the body (Col. 1:18).
It will prove difficult for us to spread the true message about the church if we don't choose to be careful to honor its Biblical representation. The church of Christ does not have a doctrine, the Bible is doctrine. The church of Christ does not have a position, the Bible has a position. The church of Christ does not believe…, the Bible teaches... When we come into a proper appreciation for these simple ideas, we will help ourselves and others become obedient to Christ in a unified fashion and exalt the name of God and His church.
There is no greater institution on the earth than the church of Christ. It is the kingdom of God (Acts 1:3). It is the body of the saved (1 Cor. 1:18). It is the family of God (Eph. 3:15). May we always strive to love our God and the church He sent the Son to establish! May we always properly represent this sacred body of sanctified people!

– “Now to Him who is able to do far more abundantly that all that we ask or think, according to the power at work within us, to Him be glory in the church and in Christ Jesus throughout all generation, forever and ever. Amen” – (Eph. 3:20, 21).