They call it a complaint because that's the technical terminology. 

Criminal complaint: Criminal complaints are the way some criminal prosecutions start. They're "accusatory instruments," that is, they're the papers filed in the courts that charge or accuse persons of committing crimes. 

Complainant: A person, group, or company that makes a complaint, as in a legal action.

Sorry to hear of your theft issues. With the law changes things are only getting worse. It sucks.