I recently let my StraightTalk (ST) expire and switched to ConsumerCellular (CC) keeping the same phone number. CC asked that I keep my ST SIM in until the phone quits than put in the CC SIM. Well it has been over a week since my ST account expired, I confirmed on the ST site my SIM is deactivated, however, everything is still working. I have not tried my CC SIM yet. Both CC and ST are re-sellers of AT&T; is it possible I am getting my CC service through ST SIM? How can you tell who is your provider?
Put the SIM you want to use in your phone, then go into the settings, network connections, more connections, and check the APN settings. As long as your phone is unlocked or compatible with your SIM, you should see an option (or multiple) for the provider you want to use. When you're on the lockscreen or you drag down your notification menu, the carrier name is typically visible as well.