They're "people who go to the same church as I do". If your church has parishes you might refer to them as "fellow parishioners", and there are likely other terms specific to different religions.
1 I would use parish or parishioners. Otherwise, I think that Margana's congregation is another good choice. According to Collins: parish noun 1) a subdivision of a diocese, having its own church and a clergyman related adjective parochial 2) the churchgoers of such a subdivision
More likely would be "calling on" visitors/prospective parishioners. Contributing to the demise of this usage — even beyond the telephone — is the expression "pay a call on someone," which subsumes the use of "call on s.o."
To clarify the answer: A Minster is a Church that has priest (s) that administer to and visit the parishioners. It is open to the public for worship. A Cathedral is a Church in which the throne of an Archbishop is located. An Abbey was originally a Church that was used exclusively by monks. It was not open to the public for worship.
Anyone whose employment, recreation, or other purpose required extensive walking could also pound the pavement — “sandwich men” (sandwich board advertising), newsboys, letter carriers, salespeople, union organizers, people canvassing for an election, clergy calling on parishioners, and —the most frequent usage today — people walking ...