http://youtu.be/UhhMFF4a6fk Video instruction!
Simple and easy for usage 2waysms messenger. This wordpress plugin allows you send bulk or single SMS messages and receive SMS answers to your SMS Number.
http://wordpress.org/extend/plugins/2-waysms-messenger/
http://downloads.wordpress.org/plugin/2-waysms-messenger.zip
Upload 2-waysms-messenger folder to the /wp-content/plugins/ directory
Activate the plugin through the 'Plugins' menu in WordPress
Go to 2-WaySMS Settings in admin...