Hmm thats a real odd one.
the filters should take out the ADSL noise assuming you've connected them up correctly so that the phone is on the filtered side (and by the sound of things you've already got that covered)
Wander if theres a fault on the DSLAM/Line somewhere, sounds like your going to have to report a fault although i'm not sure if you'd need to take it to your ISP as a broadband fault or your Telecoms provider as a line fault
Tell them that you've already tried new filters.etc
Don't tell them about the New master socket/junction box as your not really supposed to do that yourself.