This policy setting allows you to specify if the user can send and receive SMS and MMS text messages. Note that this policy ...

"This policy setting allows you to specify if the user can send and receive SMS and MMS text messages.  Note that this policy setting affects only built-in SMS and MMS applications. To prevent users from sending and receiving SMS and MMS text messages using a third party application, you must restrict application execution by configuring the Application Disable policies or by configuring Security Policies to allow only those applications that are signed by trusted authorities to run.  If you enable this policy setting, then the user cannot send or receive any new SMS (with Type = Text, class 1, 2, or 3; Type = Raw; and Type = vCard) and MMS text messages. The user can view existing messages, and continue to receive special types of SMS messages that are not blocked, even if this policy is enabled. Note that the user may be charged for any SMS messages that are blocked by this policy on the device.  If you disable or do not configure this policy setting, then the user is able to send and receive SMS and MMS text messages."