Idea of SMS Icon
This is a speech bubble. The speech bubble is in the shape of a rectangle with rounded edges and a little comma on the bottom left that would point towards the speaker. Inside of the speech bubble are 3 circles in a horizontal line.
This page contains the SMS vector icon, as well as variations of this icon in different visual styles, and related icons. All icons are in the flat vector style, however, differ by the line thickness, fill, and corner radius.