Agents must be assigned with an identity that is linked to a channel before they can send messages on that channel. Typically, these identities are based on the channel and take one universal name on behalf of the company.
For example, on Facebook and Messenger, the identity is the name of the page. When the agent replies to a message on that channel, the reply identity is the name of the page. If messages are posted on the Support page, the identity used to reply will be Support.