Well, you're correct.....phone harassment is "Illegal" in all States. You do not mention having any idea WHY this may be happening all of a sudden?
Have you checked with friends & neighbors to ask if they too, are being inundated with what you call, "spoof calls?"
If you have caller I.D. feature: Save the "log" with numbers &/or names, date, time & duration of calls. If you do not have this feature, keep a pad and pen near your phone to manually document this info, each & every time it occurs.
First things, first. GO TO your Police Dept. and file a formal complaint.
Your next communication should be with the phone Co. Inform them of the situation and that you have filed with local police. 98% of all Phone Companies take these matters seriously and should be willing to help you with a solution. (If & when the guilty parties are exposed, you need to be 100% willing to press charges.)......In other words, you need to hope it's not a friend or family member.....because they will face legal action, regardless.
Take action asap. Good Luck. Please let us know how this ends up for you.....Peace, Paula