If your team is working with multiple inboxes and different channels (e.g. sales, support, etc.) and you want to limit the outgoing channel to the corresponding inbox, you can follow these steps:
1) Go to "Channels", select the channel you want to associate with an inbox by clicking on "Edit", check the option "Assign to team mailbox" and select the desired mailbox.
2) From settings, go to "Team & permissions" and check the option "Limit the channel to the assigned mailbox"
3) At this point, from the "Conversations" section, selecting a specific inbox, you will be able to send template messages only from the number to which the inbox is assigned.