They can track the tel num via the provider. I would be asking them to do so.

You shouldn't have to go through this.

Do not talk to them just hang up and take the phone off the hook. Or get a whistle and blow hard down the phone then hang up, again then take the phone off the hook.

I am surprised they did not give you any advice, that is not right. I would make a call to the police station complaining about this.

Change your number as soon as you can and for the time being do not give it out to anyone.

Keep a record/log of each phone call this will be able to confirm who it is calling you. And if this goes to court then it will be used to compare to the actual phone bill records.

Personally I get hold of the name of one particular police officer and phone them every time I had a nasty phone call. If you are harassing them then perhaps they will know how you are feeling.

Good luck with this .