Block Inbound Phone Number

Ask Retell Partners
1

Is there any way to block some inbound phone numbers?

There are some people using the inbound to spam the agent, and it’s just piling up the billing.

2

@admin19 - Yes, if you store the spam numbers in a CRM, Google Sheet, or database.

At the start of the call, do a check to see if the number exists in the spam list.

If it exists = end call.

If it does not exist = continue.

3

Is there anyway we can block it through Retell, let’s say If we have Spam list or IF we assign"do not contact" as yes, the inbound will not be activated

4

@admin19 - I don’t believe Retell has this feature, but if I were facing this issue, I’d follow the method above using the inbound webhook to filter before the call connects.

This way, you can filter out the spam callers from whatever database you like within 0-1 seconds of the call connecting.

EDIT: Retells new contact feature does have a ‘do not call’ field.

Screenshot 2026-07-06 at 12.44.34 PM
Screenshot 2026-07-06 at 12.44.34 PM1556×809 50.2 KB

However, in the conversation flow agents, there does not appear to be any way to filter for this.

5

@admin19 - sent you a message

6

Yeah trus, I need to submit this as feature request since spam call to AI has growing so far

7

Here’s how I would go about it, hope this helps:

Phone number setup

  • Disconnect the inbound AI agent from the phone number
  • Leave the inbound webhook attached to the number, with no inbound agent assigned

When an inbound call comes in, Retell fires the webhook with the caller’s phone number.

In n8n (or equivalent)

Stage 1: check whether the caller’s number exists in your spam database, then branch into two paths:

Path 1: Spam record found

Respond to the webhook with a 200 and an empty call_inbound object. This rejects the call before the agent answers:

{
  "call_inbound": {}
}

Path 2: No spam record found

Respond with a 200 plus override_agent_id and any dynamic_variables. This connects the caller to the correct agent:

{
  "call_inbound": {
    "override_agent_id": "agent_12345678910",
    "dynamic_variables": {
      "first_name": "{{ $('Search Contact By Phone').item.json.contacts[0].firstName }}",
      "time_plus_date_right_now": "{{ $json.currentDateTime }}"
    }
  }
}

Result: spam callers are auto-rejected before the Retell agent answers, and legitimate callers are routed to the right agent.

2 Likes