To insist that the phrase "break bread" in Acts 20:7 refers to the Lord's Supper is to go beyond what is written. This is a possible meaning, but it is by no means certain.
This meaning is often arrived at by circular reasoning:
A. The claim is made that the church met on the first day of the week to have communion.
B. How do we know?
C. Because Acts 20:7 talks about meeting on the first day of the week to break bread.
D. How do we know this "break bread" refers to the communion?
A. Because that's what the church did when they met on the first day of the week.