The Plugin SMS User Limits is for setting limits on a per user per day basis.
It currently works with the following SMS providers:
Access SMS.
Voodoo SMS (version 1.0.2.0).
Ice Trak SMS (version 1.0.6).
This plugin is available form the RDB Store:
Click Plugins and then click RDB Store.
Log into the store (Decision makers and verified users on the members area only).
Search for the plugin and click Install.
Assign the plugin to appropriate users.
Once this plugin is installed it can be found through Plugins , SMS limits and limits for users can be added to it.