many phones just have "text message" in their user interface and send as SMS or MMS, just as reqired. my SE phone does this: when i write an SMS there, it shows me all the options to attach images, videos, sound files etc. - it'll technically send it as an MMS then but wouldn't let me know. there's not even a choice in the UI for "send MMS". (which, btw, also means i can never send a plain text MMS from this phone, even if i wanted to for whatever weird reason.)