Keeping a call from being traced is known as call blocking. Using a call blocking service prevents users with caller ID from seeing the name and number attached to the phone. Law enforcement agencies can trace the call, but will require a warrant to do so and will only trace the call if threats or other illegal topics are discussed during the call. One call-blocking method involves dialling "*67" before the call.
Pick up the handset to the phone and listen for a dial tone.
Enter in "*67" and wait for two beeps or a second dial tone.
Enter in the number that will be called. The receiver will not be able to see the name or number of the person calling.