I would bet that the underlying carrier keeps records of calls (Tracfone is an MVNO using other carriers networks to provide service). If you have the phone number (identifies the underlying carrier and caller), that is all that they would need to look up the records. Unfortunately, you need to get the police involved somehow to get the records needed to prosecute. If the police won't help, call the District Attorney's office and talk to them. If you have the caller ID records that would help. If that goes nowhere, call the State Attorney General's office and if these are interstate calls, the FBI.
The calls may need to be traced because Tracfone does not require name, address, etc. to activate and a false name may have been used if the owner did provide info.
Another tact is to have a friend unknown to the harasser call him (blocking caller ID), claiming to be from the FBI and telling them that if the harassing calls do not stop that he will be arrested, tried and convicted of stalking.
The tact I prefer is to give him a taste of his own medicine. Using obscene language, tell him to go f--- himself among other tasteless remarks. PM me if you need ideas. This will also use up his minutes, leaving him no way to harass you until he loads up! If you are sure of the person you could also spread nails in his driveway, throw eggs at his cars (wrecks expensive paint jobs), flatten his tires by popping them with a jackknife, cut his spark plug wires (disconnect them first) etc. Do not get legal authorities involved if you go this route!