Deactivate a brand/campaign registration

Terminates the campaign with the carrier registry so the recurring monthly campaign fee stops (carriers bill the first 3 months of a campaign regardless). Numbers covered by it can no longer SEND texts — receiving is unaffected — until they're registered under a new brand. Irreversible: a deactivated campaign cannot be restored; texting again later requires a new registration (new one-time and review fees). Idempotent.