Who can do anything besides advise you what to do, you have more power to stop them than anyone on here does? If you've got a cell phone, try finding a call blocking app that stops all private, unknown callers. For a landline, consider a call blocking device, blocking the number yourself, or turning off any answering machine and letting the phone ring with mystery calls. If they're calling after hours, try shutting off the ringer or disconnecting the line if you can manage without. They get tired of calling numbers they get nothing from and give up eventually. It takes patience and doesn't happen overnight.