> ## Documentation Index
> Fetch the complete documentation index at: https://docs.paypathiq.com/llms.txt
> Use this file to discover all available pages before exploring further.

# contact_update_unsupported

> Contact update unsupported (HTTP 409).

| Field          | Value                                                            |
| -------------- | ---------------------------------------------------------------- |
| Status         | `409`                                                            |
| Problem `type` | `https://docs.paypathiq.com/problems/contact_update_unsupported` |
| Retryable      | No                                                               |

## When this happens

The request changes a Customer's `contacts`, but at least one existing or submitted Contact has no `externalContactId`. PayPathIQ can only match Contacts by their external ID, so it cannot tell which Contact to update.

## What to do

Send an `externalContactId` on every Contact. Contacts that were created without one cannot be changed; repeat them unchanged or omit `contacts`. See [Updating Contacts](/concepts#updating-contacts).