All phones ring at once on my MicroCell

That is very odd and something I have not heard of before. Does that happen if you are out of MicroCell range? Do you have any sort of call forwarding setup on the phones by accident? I'm assuming that only one phone number is the primary number (account holder) and the other two are Approved Users (different AT&T accounts).

Approved Users do not need to have different AT&T accounts, they just need to be AT&T phones.

Actually, I have personally experienced this a few times.  My wife's iPhone and my iPhone both rang at the same time when her parents called the other night.  I have updated to iOs 8.02 and my wife has also.

I don't know if this truly solved my problem but I found that the iPhone Facetime settings on my iPhone showed checks by both my iPhone's phone number and my wife's iPhone phone number, saying that I can be reached at either number.  I unchecked my wife's phone number and this hasn't happened since.

Her parents weren't trying to make a Facetime call though.  We were both connected to the Mcell at the time.  It was strange and I'm watching to see if it happens again.

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@Avedis53 wrote:

Approved Users do not need to have different AT&T accounts, they just need to be AT&T phones.

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What I meant, and probably wasn't clear, is that the other phones just have to have an AT&T cellular account, which I guess would imply an AT&T phone.

I haven't experience what Avedis53 has on our iPhones, but only one of them is a 5 runing iOS 8.0.2, the other one isn't so maybe it's a default setting that got changed with the update?

That was it! Here I was blaming the MicroCell. We share the same Apple ID and are on the same WiFi network.

Knowing what to now search for, I also found this article on how to disable this feature:

http://www.gottabemobile.com/2014/09/30/stop-all-iphones-ringing-ios-8-call-from-your-iphone/

@GeekBoy -  We all have separate Apple ID's, but are on the same WiFi network, so the Apple ID didn't even occur to me. Thanks!

We were both connected to the same Wi-Fi network and both iPhones use the same Apple ID.

As a follow-up, I did notice that when I upgraded to 10.9 on my Air, whenever my laptop is on, and someone either iMessages me or FT's me, a notification on my laptop would appear as well as my iPhone ringing/beeping because both are tied to my Apple ID. So it's just "my stuff" that goes off simultaneously if all is on at the same time.

I experienced the same issues with 3 iphones sharing one icloud account when on the wifi network in my home. This doesn't seem to have anything to do with the microcell. This started happening after an upgrade to ios8. 

I saw an article here:

http://www.gottabemobile.com/2014/09/30/stop-all-iphones-ringing-ios-8-call-from-your-iphone/

and disabled the following setting:

Settings -> FaceTime -> iPhone Cellular Calls 

That has stopped all of our phones and ipads ringing at once when we are at home. I don't see any negative effect (that I am aware of) by disabling the setting. All phones can still make and receive calls, but now all phones are not ringing at once.