Open a dispute against the claim's resolution with the carrier. Provide a
reason (e.g. "Proof of Delivery" or "Proof of Value") and a supporting
note — both are required, and a missing field returns 422. Only one
active (pending or in-process) dispute may exist per claim at a time;
attempting to open a second also returns 422. Optionally upload evidence
images (jpeg/png/tiff, max 3 per claim, 5 MB each) via attachments[];
a disallowed or invalid image rolls back the dispute and returns 422.