It is imperative to include an opt-out/unsubscribe function in any broadcast SMS message, especially if it's promotional in nature.
A popular option is to include the phrase "Reply STOP to OptOut" allowing the mobile to reply via text.
Alternatively, you can use the [[STOP]] command to insert a clickable link, for example "Click [[STOP]] to OptOut".
When sending to an opted out mobile number, the SMS will fail with the result "Destination is blacklisted" and you will not be charged.
TNZ's SMS service includes an automated unsubscribe tool.
When a SMS is received that begins with 'stop', 'optout' or 'unsubscribe', the mobile number will automatically be added to your Dashboard Opt-Out List.
You can view the list of opt-outs at Dashboard Opt-Out List.
Using the Dashboard Opt-Out List tool, you can manually add opt-outs.
You can also add a mobile number to the list under View Messages | SMS Received, checking the box next to the received message, and clicking Create.