BT Fault

I have a fault on my phone line that results in a loud crackling noise on the speech circuit. ADSL is fine.I question what it has to do with my ISP, BT Yahoo broadband.Ah,well,you have an ADSL faceplate fitted (by BT 4 months ago) on the master socket and the fitting of the plate was instigated by your ISP,which it was following an ongoing BB problem at the time. I have been told by this engineer that I have to contact my ISP before anything more can be done. BT Yahoo internet 151 say it is an undergound fault external to my home.