Copper wire oxidising

Hi all,
The connection for our phone (the plastic bit on the wall that the phone plugs into?) keeps getting the green build up on the stripped part of the wires and causes a constant crackling on the phone. I have cleaned it a few times (just by scraping or cutiing back to expose new wire) but it comes back quickly. There doenst seem to be any dampness or other obvious things to do- can i coat the bare wires with anything to stop this??
thanks
Robert

This may sound silly, but a thin smear of Vaseline works for me. Just make sure that the connection is tight enough for a good contact to be made.