I had the same fault of crack line on the phone line, provided through Sky. I tried all the tests as instructed by Sky, and by Openreach, no change.
Even paid for Openreach to reroute the incomer around the outside of the house and install a twin outlet master socket. Still the same crackling on incoming and outgoing calls. Openreach came again an ‘checked’ the line back to the local switch panel. Openreach reported ‘no fault on the line’
Still the crackling persisted.
The solution was to open and clean out the BT junction box on the front of my house, brush out the dust and sand gathered all around the wiring, spray the whole scenario with GT 85 with PTFE, a lubricant, penetrator and water displacer. The same solution I used to use for a misfiring mini ignition.
Bt Openreach, I can demonstrate if you need to learn a trick or two.
nomorecrackling74 , 25 November 2020
Its not BT Openreach, its just Openreach now.
Openreach look after the external network, for most providers, apart from Virgin Media.
The junction box would belong to Openreach, not the Service Provider.
If you are unhappy with the service provided by Openreach, then you can complain via your provider.