I just purchased the Galaxy S21 Plus, and I'm having trouble receiving text messages from my wife's android cell phone while I'm at work. The only way I can receive her messages is if I turn on data. My old Galaxy Grand Prime could send and receive text messages with the data turned off while I was at work. Any suggestions? I'm a 65 year old that doesn't know too much about these gadgets and could sure use some help.
It might be because you have the new Google Chat (RCS) feature turned on in the Messages app. If you are using the Samsung SMS app has a RCS equivalent feature.
Either way RCS has enhanced features that require data/ WiFi to work. If the app detects that both the sender and receiver has it enabled then it will use it over regular SMS from that point on, even if one side has days turned off.