You can determine whether the problem involves inside or outside wiring by performing a simple test on the Network Interface Device (NID).
What's a Network Interface Device (NID)?
A "NID" is the box where the inside wiring connects with the outside wiring.
It's usually attached to the outside of your house or building where other utilities, like your electric meter, are located. Look for a rectangular plastic box. It's gray, but customers sometimes paint it to match the color of the house or building. Occasionally, an outdoor-type NID is located inside a basement, garage or utility area of the house.
Apartments or condominiums may have an indoor-type NID, which is usually a special phone jack located in the kitchen.