The average CS representative of the average ISP/CP is bound to get the "wrong end of the stick" and insist that you do "this, that and the other", exactly as written in the script, from which they would be reading!
If you report that you have performed a quiet line test, with a wired telephone connected directly into the "test socket" at the NTE5/A, and the result is significant audible noise, then you have covered everything -- leaving the ISP/CP with no "wriggle room"!