Questions about phone calls

The phone company would be able to trace these calls even if calling number forwarding is turned off. Same goes for mobile phones (cell phones). They would also be able to tell where the cell phone is, by reference to the aerial or mast the cell phone is connecting to the PSTN (public service telephone network.) through.
You could make things a little more difficult by using incoming call diverts, perhaps even setting up a chain of them. The thing is with modern phone systems it's practically impossible to hide.

You could just have them use public phones; almost every convenience store has a "drive-up" phone booth these days.

Any phone call made, from anywhere, to anywhere, can be traced by the phone company. As for cell phones, finding their location takes more work, but any call that connects leaves a trail with their number - so the phone company can tell you what number called and how long or short it was connected. They can also trace the owner of the phone (unless it's a disposable cell phone) and the location (land lines right away, cells take triangulation and a slightly longer call-connect time)

If you want them to NOT be found, use Alleycat's suggestion of a pay phone. The phone company will know which pay phone it was, and what time the call was made, but of course by then your hicks have hoofed it.

Depending on their financial means (unless you want them to steal some) the could use disposable cells and pay cash for the minutes.

I also wanted to add that for the phone company to release information on a harassment situation they require a complaint number and report from a police department. Then I believe they release the information to the person being harassed or they may release it to the police agency directly...I would have to check for sure. If you'd like me to, please PM me and I'll check further with someone from work.

Without the complaint number and report the information is considered confidental. They will not release it to the complaintant until a police report is made.

Southern, if it's helpful, I'll explain briefly a real life situation.

About two years ago, I began receiving harassing phone calls, mostly in the middle of the night. The caller ID did not show the number or person, only "Private Caller." I complained to the phone company, and they gave me a code to use on the key pad after each call (*57, I think). After three such calls, they would release the caller information to police if I made a complaint.

The next day, I received seven more calls. A police report was made, and the phone number and name of the caller were released to an investigating officer. He went to the person's home. It turned out to be my daughter-in-law, who was angry with me and felt this was a fine way to express her displeasure.