No, all calls are traceable but probably not by you. The police, FBI, CIA all have methods to trace calls. Did you know your cell phone calls are on an open frequency that anyone with the right equipment can listen to.
By doing the above, or contacting your service provider and tell them you want caller id privacy then whenever you place a call if will show as private, unavailable, incoming call, etc. You may want to set your cell phones GPS settings to restricted or by permission only (if so equipped), allowing only 911 or law enforcement access. There are also devices and software available that you can purchase that block traces. Although no matter what you may do, someone will be able to trace you. The government can trace any cell call you place within a couple hundred feet of the tower your cell uses at the time of the call. They cannot do that without a subpoena or court order, although the patriot act has made for some pretty loose loop holes regarding that issue.
Well this sound really creepy.....I've never heard of untraceable but I know if you use *67 it will show up as a private or blocked number on a caller ID.