How to block my kids iphone from my neighbors open Wi-Fi?

I have locked down my wireless router but my new neighbor has their Wi-Fi open. I'm trying to limit Wi-Fi usage at night and I have done everything other than take the phone and would like to know if there's a way to block my children's iPhone from the open Wi-Fi.

I think the best solution is to go around to your neighbours house and let them know that they need to put a password on their Wi-Fi modem. They probably don't realise that other people can access it so they would appreciate you letting them know. That is a sure way to stop your son using it at night or anytime. Also explain to your son that it is wrong to do that because it slows down their internet speed and they also are paying for it. I can understand why someone would go on a neighbours Wi-Fi if it's unprotected and I'm sure you can too so don't be harsh to him but make sure he understands why it is wrong so he might think twice other times too.