Why do I need to confirm my phone number to send a group SMS? I am using the Android Messages app to send an SMS to more than one person at a time. I get prompted with a message that &quot;Messages needs your phone number&quot; and a button labelled &quot;Fix&quot;. I then get this dialog:

I have two questions:

Why does Android Messages need my phone number? Doesn't it know it already? Will I have to change it later if I change SIM card? I don't get this prompt when sending an SMS message to one person.

Is Android Messages doing something other than sending normal SMS messages here?


I'm using Android 6 and the latest version of Android Messages from the Play store.
Had the same problem, I know my phone number is on my SIM because enabling DSDS and toggling on eSIM displayed my phone number under the right carrier.  I turned this all off, but at least I knew my SIM wasn't messed up.

I used dialing code *#*#4636#*#* to look at Phone Information.   Even this menu showed my phone number as unknown!

I used the ellipsis menu on the Phone Information screen to Select Radio Band and set it to United States, which seemed to kick the connection to my carrier and now my phone number is showing up and messages doesn't nag.