Perhaps not everyone knows, but all SMS you enter a title (in the ‘Subject’ field) automatically turns a MMS and therefore, you are charged for this even if you do not include any image, video or audio files.
So, if your intention is just to send an SMS, never use the Subject space, to avoid surprises in your cell phone bill. ?
If the “Subject” field does not appear for you, go to Settings> Messages> Show Subject
GordoGeek Tip