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# How to use the caller ID prefix filter for geo-routing

||| Available on Marketing and Agency plans only.

The **Caller ID Prefix** filter reads the first digits of an incoming caller's number (country code or area code)
Then, it routes the call to the destination you assign to that prefix. 

This powers **Geo-routing**: the ability to send callers to a local office, regional team, or franchise branch based purely on where they're calling from.

**Common use cases include:**
* Routing Chicago-area calls (312) to a Midwest sales team.
* Sending UK callers (+44) to an international support line.
* Blocking entire country codes from reaching your numbers at all.

### How Geo-routing with Caller ID Prefix works

When a call arrives, Nimbata checks the caller's number against the prefixes you've configured. If there's a match, the call follows the path you defined for that prefix. Any number that doesn't match a configured prefix follows the default "remaining" path — which you also define.

| You can configure as many prefix routes as you need. Prefixes can also be used to route anonymous calls, send certain regions straight to voicemail, or hang up immediately.

### Step 1. Open the Call Flow Builder

* Go to [Tracking > Call Flows](https://app.nimbata.com/tracking/call-flows).
* Click **+ Add** to create a new call flow.

### Step 2. Add the Caller ID Prefix filter

* Click the **+** button on the canvas.
* Select **Caller ID Prefix** from the Filters menu.

![](https://storage.crisp.chat/users/helpdesk/website/-/2/f/4/5/2f459a49cf382400/image_1tgrs3b.png)

### Step 3. Enter the prefixes you want to isolate and define what happens to them

* Type the country codes or area codes you want to handle differently into the prefix field.
* Click the **+** below that branch and select the routing action for those callers (e.g. **Hang Up**, **Voicemail**, or **Dial** to a specific destination).

![](https://storage.crisp.chat/users/helpdesk/website/-/2/f/4/5/2f459a49cf382400/image_1fm699n.png)

### Step 4. Define what happens to all other callers

* Click the **+** button on the remaining-callers branch.
* Select the routing action for everyone who doesn't match a defined prefix.

![](https://storage.crisp.chat/users/helpdesk/website/-/2/f/4/5/2f459a49cf382400/image_2pjfo3.png)

### Step 5. Add additional prefix routes as needed

* Repeat Steps 3-4 for each additional region or country you want to handle differently.
* Connect each new prefix branch to its appropriate routing action.

![](https://storage.crisp.chat/users/helpdesk/website/-/2/f/4/5/2f459a49cf382400/image_hmcav7.png)

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🎉 Your Geo-routing call flow is set up. Assign it to tracking numbers under [Tracking > Numbers](https://app.nimbata.com/tracking/numbers) to go live.
Detailed Guide: [**How to block calls from specific countries**](https://help.nimbata.com/en/article/how-to-block-calls-from-specific-countries-gnh58r/) 
Detailed Guide: [**How do I handle anonymous calls without losing any leads?**](https://help.nimbata.com/en/article/how-do-i-handle-anonymous-calls-without-losing-any-leads-uomzi0/) 
Detailed Guide: [**How to assign tracking numbers to call flows**](https://help.nimbata.com/en/article/how-to-assign-tracking-numbers-to-call-flows-uxu7qb/)