The icon is a logo for the Callback Feature. The icon is what appears to be the shape of an old phone. The phone is at an angle with the top of it to the top left. There is a curved arrow that starts at the mouthpiece and points to the top.
This Callback icon is made in Material Design style
developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 5,700 icons, all in the same style and quality.