warrant on me for harassment. Is this guy real? It's been four months and nothing has happened...
Sounds like bullshit. You would get a summons in the mail first, or they would come see you in person.
They don't typically call or text you to warn you they are coming to pick you up that would be stupid for obvious reasons.
Also I don't know where you live but afaik you don't get an arrest warrant for a harassment complaint.
Almost certainly bull. You can contact your police department to see if they have a warrant out on you possibly. If they don't you could file a police report and give them the record of the text/phone number and they may decide to go after whoever it was for impersonating a police officer though.
The way warrants work in my city is that you must confirm it in person.