Dialing *77 on an iPhone activates Anonymous Call Rejection, a carrier-supported feature that blocks incoming calls from people who hide their caller ID. If your carrier supports it, these callers won’t reach your phone and will hear a message asking them to unblock their number and call again.
How Anonymous Call Rejection works
When you dial *77, you're enabling a network-level service called Anonymous Call Rejection (ACR). Once active, any caller who has blocked their caller ID — appearing as 'Private,' 'Restricted,' or 'Unknown' — will be automatically rejected before the call reaches your iPhone. Instead of ringing, the caller hears a recorded message stating that anonymous calls aren’t accepted.
This feature doesn’t block all unknown numbers. It only stops those who actively hide their identity. Numbers that appear normally, even if unfamiliar, will still come through. The rejection happens on your carrier’s network, not on the iPhone itself.
Carrier support and limitations
Whether *77 works depends entirely on your carrier. Traditional landline providers and some older digital networks support it, but many modern cellular carriers, especially those using Voice over LTE (VoLTE) or 5G Voice over New Radio (VoNR), no longer support vertical service codes like *77.
If your carrier doesn’t support the feature, dialing *77 may result in a fast busy signal, an error message, or no response at all. Prepaid and mobile virtual carriers are less likely to offer this service. There is no universal list of supported carriers, and support can vary even within the same provider based on account type or region.
Difference from iPhone’s Silence Unknown callers
The iPhone has a built-in setting called 'Silence Unknown Callers,' found in Settings > Phone. This feature sends calls from numbers not in your contacts, recent calls, or Siri suggestions directly to voicemail. It’s different from *77 because it doesn’t distinguish between hidden numbers and unlisted ones, it treats all unfamiliar numbers the same.
Anonymous Call Rejection (*77) only blocks calls where the caller has intentionally hidden their ID. Legitimate callers with visible numbers, even if you don’t recognize them, will still ring through. This makes *77 more precise for blocking hidden callers without missing calls from businesses or services.
How to turn off Anonymous Call Rejection
To disable *77, dial *87 on your iPhone. This turns off Anonymous Call Rejection, allowing calls from hidden numbers again. Like *77, this code only works if your carrier supports it.
Because the feature is network-based, turning it off requires another network command. It won’t change by adjusting settings on your iPhone or toggling features like Do Not Disturb. If *87 doesn’t work, contact your carrier to confirm support and check your account settings.