Why do I get a text message on my iphone, and how can I change it back?

1. If the other party is not using iphone or imessage is not turned on, then you must have received the SMS.

2. If the other party is using an iphone, and imessage is turned on, but imessage is not turned on on your iphone, then you will also receive a text message;

3. Check whether your imessage is open, if not, please open it;

4. The functions similar to facetime are the same and need to be turned on by both parties.