It's all a game these days.
You report the line as noisy to your CP, their test says battery contact, they raise a fault with Openreach.
Openreach clear the battery fault, but to you the fault remains because it's an HR causing the noise, the battery was non service affecting.
You raise the fault again, but now when your CP tests the line it tests OK to SIN349. So your CP, rightly or wrongly, raise the cheapest option with Openreach they can, a CDTA task (conscious decision to appoint) The engineer is tasked to attend site, carry out a PQ test from the NTE and listen on the line with their test phone. (Your BB kit unplugged means the noise is gone) These tasks are raised as a gamble by the CP ..... it tests OK but our punter says it ain't ... We'll agree to pay Openreachs charges if the line does pass a PQ test and the engineer states no noise.
To receive one of these tasks is a lottery, when you turn up the punter is often trying to report something different (usually a broadband fault) or they want the line shifting, or there's a fault on their extension wiring, etc, etc.
The CP hopes the engineer is dumb enough to just resolve whatever issue the punter IS actually reporting (bear in mind they are the only people who actually
meet and deal with the punters face to face) and thus Openreach foots the bill for wasted engineer time. They are HOT on these tasks, scrutinised greatly to ensure that every opportunity to raise revenue is taken (and why not, they only get tuppence ha'penny a year in line rental)
As I said, it's all a game. Maybe if the industry was awash with revenue this wouldn't be the case, but regulation and the nations incessant quest for the absolute best for absolutely sod-all means that industry fights and squabbles, makes unreasonable demands with dire consequences for perceived failure, and all to the detriment of what the punters actually receive.