The Cancel Messages option, when used at the base Carriers tree, allows you to cancel messages for all carriers. If you right click on a specific carrier and select this option, it will only cancel messages for that specific carrier.
•Cancel all past due messages
Enabling this option will cancel past due messages. Past Due messages are Repeating Messages that should have been delivered but haven't, which can possibly interfere with the schedule of messages waiting to be sent.
•Cancel all pending messages
Enabling this option will cancel all messages in the pending queue.
•Cancel all repeating messages
Enabling this option will cancel all repeating messages scheduled by the PageGate Client.
For example, if you have a message set to repeat every hour, enabling the "Cancel all repeating messages" option will stop that message from ever happening again where only enabling the "Cancel all past due message" option will only cancel any previous repeating messages that couldn't be delivered out but will not prevent future repeating messages from being sent.