Number Pool Settings
'Use a random pool of numbers' By default, your account will send from a random pool of shared numbers. This is perfect when you're sending multiple messages to the same user.
'Use a fixed number' This will still use a shared number, but it will always try and send from the same shared number.
Note: Messages sent to the USA will always show a random number for the sender ID. If you would like a fixed number for the USA, you will have to purchase a dedicated number.