Group Texts being sent to each member individually by SMS
I'm using a brand new Sony Xperia 1 II running Android 10 and the stock google text app is sending all my group texts out via SMS individually, rather than via MMS to the entire group together.
In the Settings menu, under advanced, my Group MMS setting is not listed. If I take out the Sim Card, the Group MMS settings under Advanced REAPPEAR. My old phone (with same version of same app) still shows that setting.
I'm using a third party app, but it's crummy compared to the native one and I want to use the standard android/google apps. Is there a firmware update that will address this? Clearly it's got something to do with my SIM, given the option is there until I get onto the AT&T network.