Phone calls and texts from my phone going to DSs as wel

[Hurr1cane]

I have an iPhone and when I upgraded last year I gave my old iPhone to DS. He's 9 so he doesn't really use it all my all but it wasn't worth selling it when he could play games and stuff on it if he wanted to. He rarely uses it and can't read or anything (9, SN) so it isn't an issue: but whenever I get a phone call or text it appears on both phones so I can answer on either phone (the calls, not tried texts as he has a cheap Pay as you go sim and it isn't worth putting money on it as he can't use it)

Both phones have the same Apple ID but totally different numbers etc. I was wondering how that happens?

It isn't an issue for me obviously and it's only happened since the latest upgrade

Settings - messages - check "send & receive". You will probably see both numbers there so delete your son's number.

Phone calls you need to check under "FaceTime", again in settings.

Settings
Phone
Calls on other Devices - switch to OFF

happens all the time with DDs' phones. Apparently you can change the Apple ID of each phone but can never be bothered.

Sorry - untick rather than delete.

Thank you. I'll do that.