The SMS symbol was a dull grey circle with a paper plane and an open lock, while the encrypted message was a big blue circle with a lock in the center. You had

The SMS symbol was a dull grey circle with a paper plane and an open lock, while the encrypted message was a big blue circle with a lock in the center. You had to choose purposefully with a long press on that button to use SMS if that is what you wanted, and the recipient was using signal.