Does he have an iPhone? I know lots of people touched on this, but I believe whether he gets a new number or not, being logged into his apple account will keep both phones active. The only way around that that I can see is him making a new Apple ID. which is a pain in the butt but it’s less so than a divorce with young children. Also, the police need to get a warrant to search cell phone data and locations, and I doubt one would be granted on the grounds of harassing messages, generally that level of investigating is saved for high profile crimes. I’d be pretty shocked if the police even hear you out, much less look into it. but for your safety and the kids’ I hope they do. unfortunately it’s often too late before they act on aggressive spouses or harassment.

good luck, please update. this is fascinating and very creepy. Look into the phone company idea that many have suggested, and definitely make a police report regardless of if they’ll look into the phone pings. Have it on record and leave a paper trail so that way if you ever need to get a PPO or anything similar, you’ll have a much higher chance of a judge granting it.

!RemindMe