Is Mattias a disciple?
John 13:35 By this shall all men know that ye are my disciples, if ye have love one to another.
All men know you are Jesus disciples if you have love one to another.
I have stopped entering the local churches. Someone in the local churches tried to utterly destroy me. After that, when i refused to have any close contact with the false accuser, the church people tried to convince me otherwise. Then I separated myself from the local churches.
(II Timothy 3:2-5 [KJV])  For men shall be lovers of their own selves, covetous, boasters, proud, blasphemers, disobedient to parents, unthankful, unholy,  Without natural affection, trucebreakers, false accusers, incontinent, fierce, despisers of those that are good,  Traitors, heady, highminded, lovers of pleasures more than lovers of God;  Having a form of godliness, but denying the power thereof: from such turn away.
I think we should be believers and disciples.