Two Apple IDs, same phone number: What does that mean for iMessage?

[Synna]

Dear Community,

due to a misunderstanding, I now have different Apple IDs on my old and my new iPhone but I only have one SIM, so the phone number associated with both Apple IDs is the same. Now, I want to reset my old iPhone to get it ready for sale but I wanted to make sure that any future iMessages will only be delivered to my new phone with my new Apple ID.

Sorry if that sounds confusing, basically what I want to know is this: If I have two Apple IDs and both have the same phone number associated with it, how does iMessage work? Does it just deliver messages to the Apple ID that has active devices? If I completely reset my old iPhone by using "Erase All Content and Settings" (as described under https://support.apple.com/en-us/HT201351), meaning the old iPhone does not show up as a device for my old Apple ID anymore, does this mean my old Apple ID cannot receive any iMessages? Or do any iMessages sent to my phone number then somehow "exist" on both of my Apple IDs?

I have also read that you can remove the phone number from iMessage (as described under https://support.apple.com/en-us/HT201349), but that would also affect my current phone, right?

I appreciate your help getting out of this confusing mess. :-(

 

[ian87w]

Wait, how were you even able to assign the same phone number into two different Apple IDs? Are those actually two separate iCloud accounts? Of are you just using a separate Apple ID on your new phone and use your old SIM/number on it?

To avoid confusion, I would try to make sure your phone number is on the proper primary iCloud account that you will use. This will also better for security.

As for preparing your old phone, make sure you disable iMessage and Facetime on it first. Seems like that is the step that most people forget.

 

[Synna]

Wait, how were you even able to assign the same phone number into two different Apple IDs? Are those actually two separate iCloud accounts? Of are you just using a separate Apple ID on your new phone and use your old SIM/number on it?

I guess it's the second option you've described, I have somehow created a new Apple ID on the new phone, but I am using my old SIM/number on it. So far, I thought that this means my phone number is now associated with two Apple IDs, e.g. the old one from my old phone and the new one from my new phone.

To avoid confusion, I would try to make sure your phone number is on the proper primary iCloud account that you will use. This will also better for security.

I didn't even know that the phone number is also somehow linked to iCloud. Where would I set this up correctly?

As for preparing your old phone, make sure you disable iMessage and Facetime on it first. Seems like that is the step that most people forget.

Strange, when following the guidelines for preparing an old phone provided by Apple (https://support.apple.com/en-us/HT201351), it doesn't even mention that you should disable iMessage and Facetime. Suppose I only sign out of my Apple ID and then choose "Erase All Content and Settings" (as described in the link), is there still some connection to iMessage and Facetime left?