Let's remember that the name of the phone is the Source.

Switch to the tab "How to make changes between numbers?"

When Send Source is active, the message will contain the name of the phone.

Let's create an automation to identify the Source.

For filters, we need to add the Reply channel.

We need to identify the conversation channel.

So, if the customer replies and it contains the Source, this automation will be activated.

We can take any action, but the most common one is 'Assign To User'.

Assign to user
END
Trigger
Customer Replied contains Source: Oxxo Miguel
Add New Trigger

Before saving, we need to go to Settings.

Builder
Settings
Enrollment History
Execution Logs
Test Workflow
Draft
Publish

We need to disable "Allow Re-entry" so that the automation triggers only once.

Allow re-entry
Allows a contact to re-enter once it has left this workflow. If the contact attempts to re-enter while it is still enrolled in this workflow, it will get skipped. Also if this workflow has appointment or invoice based triggers it will allow contacts to re-enter even if the 'Allow re-entry' setting is disabled. 
Know more

Assign conversations to employees based on Source. (English)