Things You'll Need
Drywall joint compound
Latex wood filler
Electrical box cover plate
You can open the NID with a Phillips screwdriver. There may be many wires in there, and when you trace the ones you want to disconnect, you may find they share terminals with other wires. Be careful not to disturb the other wires when you disconnect the one you're removing.
If you don't want to remove the cable, it's safe to wrap the end with tape and push it into the wall or under the floor.
Although it's safe to work on telephone wiring in normal conditions, you should never do it during an electrical storm. A lightning strike could kill you if it passes through the wires while you're touching them.
A remodel may force the relocation or removal of a phone jack -- or you may be among the 30 percent of Americans who, according to "National Journal," have decided to live without a landline. Despite containing myriad wires that make it appear extraordinarily complicated, a typical phone jack is surprisingly easy to install and even easier to remove. You'll be able to do the entire removal procedure with one or two screwdrivers, but you'll probably also want to fill the holes the cable passed through. This may be as easy as moving the carpet, or it may involve some wood filler.
Unscrew the cover plate of the jack you want to remove, using a Phillips screwdriver. You don't have to worry about whether any of the wires are live; they can't seriously shock you.
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Push aside all the wires that aren't connected to anything. If your box is typical, this is most of the wires. You'll probably find only two or four wires connected to terminals.
Loosen the terminal screws with a Phillips or flat-head screwdriver, and pull off the wires connected to them. Snip the end of each wire off back to the insulation with wire snippers so that no bare metal is exposed.
Unscrew the jack from the wall and pull it off. Pull the wire out of the back of the jack. If the jack is a flush-mount type, the cable will stick out through a hole in the wall; if it's a surface-mount type, the cable probably extends up through the floor.
Find the other end of the cable. It may be connected to another jack, or it may run all the way to the network interface device, which is usually located on an exterior wall. Follow the cable to the point at which it passes through a wall or the floor on its way to the jack. It usually runs along or through the joists on the bottom floor of the house, and you should be able to access it by going into your basement or crawl space.
Pull the cable toward you, and when you have the end that was connected to the jack, pull the staples holding the cable with a flat-head screwdriver; working your way back the opposite connection point, remove the cable. When you get to the other end of the cable, disconnect it from the jack or NID to which it's connected.
Patch the hole the cable passed through with drywall joint compound, if it was in the wall. If the cable passed through the floor, use latex wood filler or rearrange the carpet to cover the hole. Some jacks are connected to electrical boxes on the wall, similar to electrical receptacles. A quick way to cover the box without removing it is to screw on a cover plate.