MMS multimedia fileName is ignored — attachments always arrive as 'Attachment.pdf'

[LitKanna]

Description

When sending an MMS with a PDF attachment via the Telstra Messaging API v3, the fileName field in the multimedia array is ignored by the carrier. The recipient always sees the file named "Attachment.pdf" regardless of what fileName is set to.

Steps to Reproduce

1. Send an MMS via POST /messaging/v3/messages with a PDF multimedia attachment:

{
  "to": "+614XXXXXXXX",
  "from": "0487XXXXXX",
  "multimedia": [
    {
      "type": "application/pdf",
      "fileName": "Pricelist.pdf",
      "payload": "<base64-encoded-pdf>"
    }
  ]
}

2. The API returns 200 OK and the MMS is delivered successfully.
3. The recipient receives the PDF, but it is named "Attachment.pdf" — not "Pricelist.pdf" as specified.

Expected Behavior

The fileName field should be honored so the recipient sees the file with the name specified in the API request (e.g., "Pricelist.pdf", "Invoice-001.pdf", etc.).

Actual Behavior

The fileName is silently discarded. All MMS attachments arrive as "Attachment.pdf" regardless of the value provided.

Tested On

• Telstra → Telstra (same carrier): fileName ignored
• Telstra → Vodafone (cross-carrier): fileName ignored
• Device: iPhone (iOS)
• API version: Messaging API v3
• Account type: Free trial

Impact

This makes it impossible to send professionally branded documents (invoices, pricelists, statements) via MMS where the filename communicates what the document is. Recipients see a generic "Attachment.pdf" which looks unprofessional and confusing when multiple PDFs are sent.

Question

Is this a known carrier-level limitation of MMS, or is there a way to preserve the original filename through the API? If it's a carrier limitation, it would be helpful to document this in the API docs so developers are aware.

Thanks!