But, when the Esp8266 is a Web Server, some simple HTML can be inserted to provide an interactive SMS interface. Because it is implemented as an HTML "form" it is interactive, and requires web user intervention.
For example:
This is a screen grab from my ERB-EspWebServer Farm.
If you are interested, check out: http://wa0uwh.blogspot.com/2015/11/esp8266-interactive-sms-from-web-page.html
Regards.
Eldon - WA0UWH