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PATCH
/
v1
/
phone-numbers
/
{phone_number}
Update phone number
curl --request PATCH \
  --url https://api.nixflex.com/v1/phone-numbers/{phone_number}
Updates the custom_prompt (business profile) on a number you have already imported. The profile is layered on top of the agent prompt as a BUSINESS PROFILE section on inbound calls and SMS replies - see Phone numbers.

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Request

curl -X PATCH https://api.nixflex.com/v1/phone-numbers/+447446466847 \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "custom_prompt": "Business: Smile Dental Croydon. Address: 12 High St. Open Mon-Fri 9am-5pm. Check-up costs 45 pounds."
  }'
URL-encode the + if your HTTP client doesn’t do it automatically: %2B447446466847.

​
Body parameters

FieldTypeRequiredNotes
custom_promptstring or nullYesThe business profile for this number. Maximum 8000 characters. Send null or an empty string to clear it - the number then falls back to the agent prompt alone.

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Response

200 OK: 
{
  "phone_number": {
    "phone_number": "+447446466847",
    "agent_id": "agent_125207e452f8714a",
    "custom_prompt": "Business: Smile Dental Croydon. Address: 12 High St. Open Mon-Fri 9am-5pm. Check-up costs 45 pounds."
  }
}
Takes effect on the very next call or text - no deploy, no re-import.

​
Errors

CodeHTTPCause
missing_field400custom_prompt not present in the body (send null to clear, not an empty body)
custom_prompt_too_long400Over 8000 characters
number_not_found404Number doesn’t exist OR belongs to a different account

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Use case: reseller end-customer onboarding

One agent template, many end-customers - each number carries its own business identity: 
// Customer edits their business details in YOUR app -> you sync to Nixflex
await fetch(
  `https://api.nixflex.com/v1/phone-numbers/${clinicNumber}`,
  {
    method: 'PATCH',
    headers: {
      'Authorization': `Bearer ${NIXFLEX_KEY_ID}:${NIXFLEX_KEY_SECRET}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({
      custom_prompt: `Business: ${clinic.name}. Address: ${clinic.address}. Open ${clinic.hours}. ${clinic.services}`
    })
  }
);
The AI answers with the new details on the next call. This is how a 200-location rollout stays one agent + one PATCH per location.