[Mt 18:15-18]:

(v. 15) "If your brother sins against you, go and show him his fault, just between the two of you

[Apparently this is done without the Church's 'infallible' authorization as it is not so specified in the passage. Notice the context is not about interpretation of the Bible but about one Christian brother who sins against another]

(v. 16) But if he will not listen, take one or two others along, so that every matter may be established

[The context continues re: one brother sinning vs another and the resolution of that situation via bringing one or two fellow believers, (and not so called church authorities), and not about the interpretation of the bible]

(v. 17) If he refuses to listen to them, tell it to the church; and if he refuses to listen even to the church, treat him as you would a pagan or a tax collector."

[church = "ekklesia" = str 1577 = assembly, congregation, {lit. 'the called out ones'} = The New Analytical Greek Lexicon, Wesley J. Perschbacher, Ed., Hendrickson, Peabody, Ma, p. 127]

[Vines Expository Dictionary of Old and New Testament Words, W.E. Vine, Fleming H. Revell Co., Old Tappan, N.J., 1981, pp. 83-84]:

"EKKLESIA.. from ek, out of, and klesis, a calling (kaleo, to call)... It has two applications to companies of Christians,

(a) to the whole company of the redeemed throughout the present era, the company of which Christ said, "I will build My Church," (Matt 16:18), and which is further described as 'the Church which is His Body," Eph 1:22; 5:23, [thus not limited to the authority within that organization]

(b) in the singular number (e.g., Matt. 18:17, R.V. marg., 'congregation'), to a company consisting of professed believers, e.g., Acts 20:28; 1 Cor 1:2; Gal 1:13; 1 Thess 1:1; 2 Thes 1:1; 1 Tim 3:5, and in the plural, with references to churches in a district."

Notice that verse 17 does not say to take it to the Pope or to some other authority in the church but to the entire local assembly of believers - the body of Christ, the Church.

Furthermore the word church = "ekklesia" is never used in Scripture to refer to a particular authority within the body of believers but to an assembly of believers - either the entire body of believers or a local congregation as it does in Mt 18. Notice then that the decision about the individual was put before the entire local assembly, i.e., congregation of believers and not some special infallible authority within the church. This continues to be corroborated in the rest of the passage:

[Mt 18:18-19]:

(v. 18) "I tell you the truth, whatever you [believers] bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.

[So it is the individual believer that has the authority to bind/loose on heaven/earth]

(v. 19) Again, I tell you that if two of you [believers in general, not church authorities] agree on earth about anything you ask for, it will be done for you by My Father in heaven.

(v. 20) For where two or three come together in My name, there am I with them."

[Asking for something from God and two or three coming together 'there I am with them' cannot be limited to authorities in the church - it must necessarily refer to the general believer = the entire context of this passage]