en_tn/mat/18/17.md

if he refuses to listen to them

"if your fellow believer refuses to listen to the witnesses who came with you"

to the church

"to the whole community of believers"

let him be to you as a Gentile and a tax collector

"treat him as you would treat a Gentile or tax collector." This implies that they should remove him from the community of believers. (See: rc://en/ta/man/translate/figs-explicit)