Phone Service - loud crackling and internet service interrupted
Sorry to hear you're experiencing problems with your phone (Which is also affecting your broadband)
Although I appreciate you've said you've tested another device and the issue is the same, could you try testing in the test socket if you haven't already and let us know if the problems are still apparent.
Is the line still noisy when testing with nothing else connected to the socket?
Thanks.
Sorry @Lethe I meant to include this in my previous response: https://community.plus.net/t5/Library/Testing-From-The-Master-Socket/ba-p/1322242
It should be the same process for pre-filtered sockets that used to be installed for fibre connections. If testing the broadband, you'll just need to use a micro-filter when connected to the test socket.
I hope this helps.
@Lethe wrote:
I'll try the phone in the master socket and see if the noise persists.
Thanks, due to the crackling on the line, we'd need to investigate and resolve that first before investigating problems with the broadband as the noise on the line could be the only cause of problems you've mentioned with broadband.
Please let us know how you get on testing the phone in the test socket.
@Lethe wrote:
The inside of my box appears to not be held together by anything. I took the screw out and the little circuit board inside is separated from the front plate. It really looks quite worse for wear. The phone is much improved when in the master socket.
When you say the phone is improved in the master socket, are you referring to the test socket behind the faceplate? Or are you generally connected to a socket other than the master socket?
Either way, I'm glad to hear there's an improvement when connected via the test/master socket, however this would unfortunately mean an engineer appointment would become chargeable if we were to send an engineer out 
@Lethe wrote:
Random side question - how do I stop the callminder service? all it does it collect messages about PPI and insulation grants.
Sorry about that, it shouldn't have actually been on your line as it's not on your account. I've made sure that'll be removed shortly for you (up to 1 working day but usually much sooner)
I meant to ask that in my previous post but it seems I forgot to.Please see picture.
When the engineer first attended to "install" the service, a new faceplate wasn't fitted - should it have been? The fact that now I've opened this as part of troubleshooting and the whole thing has disintegrated, leaving me facing a "chargeable visit" really leaves a bad taste. I ended up buying a filter for £5 - with this in the test/master/hidden socket the phone remains good quality and the internet no longer disconnects when it is in use.
Pic
Oh! You broke it, I'm telling. 
I've never really studied the box that closely before as it lurks behind the tv - the bottom and side of it looks like someone got really upset with it at some point...
My service hasn't really been great at any point since I've been here. I think now we may have finally got to the bottom of it - the old MK2 faceplate just forcibly retired itself.
Lethe wrote: (snipped) a new faceplate wasn't fitted - should it have been?
No, it's normal nowadays for the original phone socket to suffice.
The fact that now I've opened this as part of troubleshooting and the whole thing has disintegrated, leaving me facing a "chargeable visit" really leaves a bad taste.
It could have been broken by a heavy handed installer. Pushing the lead too hard into the connector can do this
It could also have been broken in error by yourself.
It would be a Harry Hill moment - "It was fitted by the installer, but used by the home owner. Which one broke it? There's only one way to find out ..... FIGHT!!".
To save an hassle, plus you don't mention any extension wiring, you've probably done the right thing with what you're doing now.
the phone remains good quality and the internet no longer disconnects when it is in use.