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.

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 handlingCall 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.

    Caller ID Prefix✕
    anonymous✕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.”
    Voicemail✕
    Ring
    DialMultipleSequentialWeightedRound robin
    Instead
    Hang upVoicemail

    Sends callers straight to voicemail.

    Voicemail Audio:
    withheld-numbers.wav1
    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.

    Main lineCall flow is valid. Assign to Tracking Number
    New Call
    Caller ID Prefix
    anonymous
    Voicemail
    withheld-numbers.wav
    Caller ID Prefix
    All other prefixes
    Multiple
    Main office, 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
Detailed guide: 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.
    Missed callsWorkflow is valid.
    Enable
    Trigger Enrollment
    Inbound CallOutbound CallForm SubmissionSMS Received
    A customer calls your tracking number
    Fires whenCall StartsCall EndsUser Updates Property
    Filter groupMatchALLof
    Call Outcomeis Not Answered✕
    Callernot equals Anonymous✕1
    Add another rule
    Action group1
    Email AlertsMissed calls✕
    Add another action
    Finish
    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

Check it worked

  • In ActivityCalls, 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 ActivityCalls. 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). If it shows a number, the call should have rung: check its Hangup Cause and see Call troubleshooting.

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, 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.