Virgin On The Ridiculous

I think I now know why Virgin bills are so high.
Over the last week the phone has been making really loud crackling noises making most phone calls unlistenable, especially a problem with the answering machine as the 10 times a day scam artists / solar panel sellers etc never leave a message but we get a recording of several minutes crackling after they put the phone down.
So called up Virgin who arranged to send an engineer, booked for an 8am-Noon slot he turned up at 1pm.
As he listened to the problem I suggested it might be related to the frayed cable between the outside box and where it comes into the house? he said it was unlikely and preceded to change the internal socket which did not fix the problem.
After spending a couple of hours changing cables and connections in our outside box, the manhole about 50 feet away and in the main box 2 streets away the problem was still not fixed.
So he arranges for a senior engineer to come around and check the various cables in the street this morning, I am sure he replaced the same things as the guy did yesterday but somehow managed to cut off our internet and TV, the phone still worked but was still as crackly as before.
Called up the first engineer to point out we still had the problem plus new ones, he couldn't explain but said he would come back this afternoon, but would also call the area engineer to come and have a look.
Before he arrived the TV and Internet came back on, although he didn't know why?
He changes the internal socket again which makes no difference, so finally he checks and repairs the short length of cable between outside box and where it comes in for the internal socket (as I had suggested at the start) and finally problem solved.
I'm not a telecommunications engineer so what do I know, but just a little bit of common sense would have suggested that might have been worth changing first? :)