Just to satisfy yourself that it is the line and not your t/p handset or some other telephonic equipment I would disconnect everything from your telephone line and extensions (if any) and then borrow another corded phone and go direct to the master socket. If you are still getting line noise make sure you get the engineer to agree with you about the noise and insist that it's fixed. It's almost certainly a dirty contact somewhere, perhaps in a junction box attached to your house or in the street.