Translation:I just sent you a text message.
Hmm. Colonials hereabouts seem to prefer single-syllable "text."
The lines are blurring, however, because the SMS app automatically switches to MMS when the character count goes over the limit.
Not many have seemed to have caught on to the joys of LINE, Skype, WhatsApp, and other chat apps—end-to-end privacy, in particular.
Only very old cell phones are limited to SMS (plain text messages). Most modern phones can send and receive MMS (multimedia messages), which allow for pictures and videos.
Today, only a technical person or someone using a very old mobile phone would need to know the difference between the two.
In the US, no one has really used the term SMS. It's always been a "text" or a "text message" when messaging directly between two mobile numbers. People also use "message" for most other platforms, such as facebook, blackberry, skype, etc.