Product: Branded Comms
When you create/update a Branded Channel resource, you send a list of your phone numbers to be associated with it. You cannot have a phone number associated with more than one Branded Channel.
At least one of the phone numbers sent in the payload when creating/updating a Branded Channel are already associated with a different Branded Channel.
Use a different phone number in the Branded Channel payload, or remove the phone number from the existing Branded Channel if you really want to associate it with the Branded Channel being created/updated.