# Calls from withheld numbers

When someone calls one of your tracking numbers with their number withheld, the call reaches Nimbata and shows in your call log as **Anonymous**, but it never rings your phone. Your phone shows nothing at all, not even a missed call. If you have a workflow that emails you about calls, you still get that email afterwards, which can make it look as if your phones are missing calls.

This page explains why that happens, and the two changes that make sure anonymous callers aren't left without an answer and your inbox only shows calls you can act on.

## Why anonymous calls don't ring

To reach your phone, Nimbata forwards each call through a telephony carrier. Our carriers don't connect calls that arrive without a caller ID, so a call from a withheld number is stopped before it reaches your destination number.

- **It isn't a setting in your account.** The block is applied by the carrier, so neither you nor Nimbata can turn it off.
- **It isn't a fault in your call routing.** Calls from callers who show their number ring through as normal, on the same tracking number and the same call flow.
- **Nobody can recover the number.** Withholding a number is the caller's choice, made on their phone or with their network. The number never reaches Nimbata, so there's no way to show it in the call log or call the person back.
- **The call is still logged.** Nimbata records the call attempt, so your reports count it and your workflows run on it. That's why an email alert arrives for a call your phone never showed.

You can't make these calls ring, but you can decide what happens to them.

**Before you start**

- Plan: Marketing or Agency (for the Caller ID Prefix filter)
- A voicemail greeting that asks callers to call back with their number showing, uploaded on the Voicemails tab of the [Media Library](https://help.nimbata.com/call-handling/greetings-and-ivr#manage-audio-files).

## Tell anonymous callers to call back

Give anonymous callers their own branch in your call flow, so instead of silence they hear a message asking them to call again with their number showing, and can leave a voicemail. Callers who show their number carry on to your phones as before.

1. **Open your call flow**

   Go to **Call handling › Call Flows** and click the call flow your tracking number uses.

2. **Add the Caller ID Prefix filter**

   - Click the **+** under **New Call**.
   - Select **Caller ID Prefix** under Filters. It splits the flow into a prefix branch and an **All other prefixes** branch.

3. **Catch anonymous callers**

   In the prefix branch's field (1), type **anonymous** and press Enter.

   [A Caller ID Prefix step with anonymous entered as the prefix, marked 1]

   *Type anonymous into the prefix field (1).*

4. **Send anonymous callers to voicemail**

   - On the anonymous branch's routing step, click **Voicemail** under **Instead**.
   - In **Voicemail Audio** (1), pick your greeting. For example: "We're unable to take calls from withheld numbers. Please call again with your number showing, or leave a message with your number and we'll call you back."

   [The anonymous branch's step set to Voicemail, with Voicemail Audio set to withheld-numbers.wav, marked 1]

   *Pick the voicemail greeting for anonymous callers (1).*

5. **Keep your routing for everyone else**

   Under **All other prefixes**, keep (or add) the routing your callers had before, such as **Multiple** to ring several phones at once. Then save the call flow.

   [The finished call flow: anonymous callers go to a voicemail, and all other callers ring the Main office and Emergency line]

   *Anonymous callers get the voicemail; everyone else rings through as before.*

🎉 Done. Anonymous callers now hear your message and can leave their number. Genuine customers usually do, or ring back with their number showing; automated and nuisance calls usually don't.

Detailed guide: [Handle anonymous calls](https://help.nimbata.com/call-handling/blocking-and-capping#handle-anonymous-calls)\
Detailed guide: [Set up and listen to voicemail](https://help.nimbata.com/call-handling/voicemail#set-up-and-listen-to-voicemail)

## Stop email alerts for anonymous calls

If a workflow emails you after calls, add one filter rule so it skips anonymous calls. You then only get alerts for calls you can see and return.

1. **Open the workflow that sends your alert**

   Go to **Workflows** and click the workflow with the **Email Alerts** action.

2. **Add a Caller filter**

   - Click the **+** above the **Email Alerts** action and select **Add filter** (or click **Add rule** in a filter group the workflow already has).
   - In the **Select filter rule** panel, under **Call Details**, select **Caller**.
   - Set the condition to **not equals** and the value to `Anonymous`, with a capital A, exactly as the call log shows it.
   - Click **OK**.

   [A workflow with a filter group holding Call Outcome is Not Answered and Caller not equals Anonymous, the Caller rule marked 1, followed by the Email Alerts action]

   *The Caller rule (1) lets the email through only for calls that show a number.*

3. **Save the workflow**

   Save the workflow. It applies to calls from then on.

> **Tip:** Only add the rule before actions you want to skip for anonymous calls. If the same workflow also transcribes or tags calls, put the Caller rule in the filter group of the email action only, or move the email into its own workflow, so your other actions still run on every call.

Detailed guide: [Missed call alerts](https://help.nimbata.com/workflows/alerts#missed-call-alerts)

## Check it worked

- In **Activity › Calls**, new calls from **Anonymous** go to the voicemail on your anonymous branch, and any message they leave is on the call.
- You no longer get email alerts for calls from **Anonymous**. Calls that show a number still trigger the email as before.

## Troubleshooting

### I get an email about a missed call, but my phone never rang

Check the caller on that call in **Activity › Calls**. If it says **Anonymous**, the call came from a withheld number, which the carrier doesn't connect to your phone (see [Why anonymous calls don't ring](#why-anonymous-calls-dont-ring)). If it shows a number, the call should have rung: check its **Hangup Cause** and see [Call troubleshooting](https://help.nimbata.com/call-handling/call-troubleshooting#calls-not-getting-through).

### Anonymous calls still send an email

- Check the value is `Anonymous` with a capital A: the rule matches the text exactly.
- Check the rule is in the filter group that comes before the **Email Alerts** action, not in another path.
- If you have more than one workflow that sends emails, add the rule to each.

## Frequently asked questions

### Can Nimbata switch off the block on anonymous calls?

No. The block is applied by the telephony carrier that connects calls to your phone, not in your Nimbata account, so it can't be lifted by Nimbata or by you. What you control is what happens to the call instead, as described above.

### Can I see the number of an anonymous caller?

No. When a caller withholds their number, their network passes the call on without it, so the number never reaches Nimbata. Ask them to leave their number in your voicemail, or to call again with it showing.

### Should I just block anonymous callers?

You can, with the [Blocked Callers list](https://help.nimbata.com/call-handling/blocking-and-capping#block-spam-callers), but some genuine customers withhold their number. A voicemail that asks them to call back keeps those leads, while most automated calls simply hang up.