It’s pretty much impossible. Law enforce will not take you seriously once they realize they have to do ‘hacker’ stuff.

Plus if the person is using a wifi hotspot or proxy server the FBI probably can’t even track them. I’d recommend just changing your phone number and only giving it to people you trust. I believe you can also have whatever anonymous text service they are using block access to your number.. if the company chooses to cooperate.

On top of that these services can be run from anywhere in the world and your local law enforcement is pretty much helpless to get logs from a company in India or such.

If you are lucky the company might just give you the IP information and you can use that yourself to get a general idea of their geography and then ask yourself who you know who lives in the area who might be mad at you. Most of the time you can guess who is doing things like this. If you feel you know who it might be maybe send them an anon text saying you know who they are or something designed to either scare them off or get them to send you another text. Basically your own little attempt at a phishing scam.

I would just give up on attempting to track them down unless the messages are worth getting a lawyer and pushing law enforcement to help. In the end I doubt most law enforcement will know what to do but you might get lucky you never know. In general most cop shops are far behind the times when it comes to tracking people online. They rely on simple tactics like mining facebook for information or getting phone records.

When a person makes themselves anonymous law enforcement basically loses all it’s normal tools and honestly if the person use a proxy server or random wifi spot even the FBI probably couldn’t track them down. Plus they can use an anon text service from another country. I doubt this person is that savvy though and there is a good likelihood the text company is located in the US, but chances are they will not release information without a court order and after that you still need their ISP to release the name associated with that IP. Technically if they are using a service in the US and you could get law enforcement to seriously go after the case you could find out who they are, but they’ll probably just put your case on file as an annoying prank and forget about it.

Change you number… problem most likely solved. If not then at least it gives you a point of reference as to who is doing it.. they’d have to be someone who knows your directly or could get your new number through a friend rather than some random asshole pranking you.