Phone use can be unlawful for the purposes not only of making threats but also by using obscene, vulgar or profane language. This crime is a class one misdemeanor punishable by one (1) year in jail and a fine of up to $2500.
The main defenses to this are identification of the caller and whether the language used falls within the nature of a threat or other prohibited language. There can also be issues of whether the call or calls ever took place at all. In some situations there are recordings of these calls which can create additional problems for both the defense and the prosecution due to the requirement to authenticate the evidence. These evidentiary issues can sometimes be complicated if the matter goes to trial. Your attorney can advise you of your options after the specific circumstances of your case are determined. With the recent popularity of texting the crime has spilled over into text messages as well as verbal communications.