How to Block Anonymous Calls on Any Phone

Anonymous calls — where the caller deliberately hides their number — are one of the more persistent nuisances in modern communication. Whether they're telemarketers, scammers, or unwanted contacts, the good news is that most phones and carriers give you real tools to stop them. The method that works best, though, depends on your device, carrier, and how aggressive you want your blocking to be.

What Makes a Call "Anonymous"

When someone calls you with no caller ID, it usually means they've intentionally masked their number. This happens in two main ways:

• Per-call blocking: The caller dials *67 before your number, which temporarily hides their caller ID for that single call.
• Account-level blocking: The caller (or their employer) has configured their phone account to always transmit as "Private," "Unknown," or "No Caller ID."

Both methods instruct the phone network to suppress the originating number before it reaches you. This is different from a number simply not being in your contacts — those calls still show a number. Truly anonymous calls show nothing identifiable at all.

Built-In Options on iPhone and Android 📵

Modern smartphones include native settings to silence or block anonymous calls without any third-party app.

iPhone (iOS)

Go to Settings → Phone → Silence Unknown Callers. When enabled, any call from a number not in your contacts, recent calls, or Siri Suggestions is automatically silenced and sent to voicemail.

This is a broad filter — it catches anonymous calls, but also any number you've simply never interacted with. It's effective but sweeping.

For a more targeted approach, Screen Time doesn't help here, but you can use the Do Not Disturb mode with "Allow Calls From" set to Contacts Only. This accomplishes a similar result with slightly more manual control.

Android

Android doesn't have a universal setting because the OS is fragmented across manufacturers. Options vary:

• Google Pixel: Open the Phone app → Settings → Blocked numbers → toggle "Unknown" to block calls with hidden numbers.
• Samsung (One UI): Phone app → More options → Settings → Block numbers → toggle "Block unknown callers."
• Other Android: Check your Phone app's settings under "Call Blocking" or "Blocked Numbers" — most modern Android builds include something similar.

The naming changes, but the underlying function is the same: drop or silence calls where no number is transmitted.

Carrier-Level Blocking

Your mobile carrier operates at the network level, which means they can intercept anonymous calls before they ever reach your device. Most major carriers in the US offer tools for this:

Carrier tools are useful because they work independently of your phone's OS, which matters if you're on an older device or a phone with limited software settings.

Check your carrier's app or account portal — the exact steps vary — but enabling enhanced call filtering usually takes under five minutes.

Landlines and VoIP

If you're using a traditional landline, anonymous call blocking is typically a feature you activate through your provider. Dialing *77 on most North American landlines activates Anonymous Call Rejection — callers with blocked numbers hear a message telling them to unblock before calling again. To deactivate, dial *87.

VoIP services (like Google Voice, Vonage, or business phone systems) handle this differently. Most VoIP dashboards include a call screening or anonymous call rejection setting in the account controls. Google Voice, for example, lets you screen calls and send unknown callers to voicemail by default.

Third-Party Call Blocking Apps

Apps like Hiya, Nomorobo, RoboKiller, and Call Control offer additional layers beyond what your phone or carrier provides. These apps typically work by:

• Maintaining large databases of known spam and anonymous call patterns
• Screening incoming calls in real time
• Providing user-reported block lists

Most integrate with iOS's CallKit framework or Android's call screening API, so they work at the system level rather than just as separate apps.

The tradeoff is that these apps usually require a subscription for full features, and they need permission to access your call data — a privacy consideration worth weighing. 🔐

What Anonymous Call Blocking Won't Catch

It's worth being clear about the limits. Blocking anonymous calls handles the "No Caller ID" case, but it won't stop:

• Calls from spoofed numbers (where a fake but real-looking number is displayed)
• Robocalls using rotating real numbers to evade detection
• Calls from numbers you simply don't recognize (which still transmit a number)

For spoofed calls, carrier-level filtering and third-party apps tend to be more effective than native phone settings alone, since they can cross-reference numbers against known fraud patterns.

The Variables That Shape Your Approach

Whether the built-in phone setting is enough, or whether you need carrier tools or a third-party app, comes down to several factors:

• Your device and OS version — older phones may lack native blocking settings
• Your carrier and plan — not all carriers include advanced filtering at no cost
• How often you receive anonymous calls — occasional nuisance versus daily harassment requires different responses
• Your tolerance for missed legitimate calls — aggressive blocking can catch anonymous calls from doctors' offices, banks, or businesses that use number masking for privacy
• Whether you use a landline, mobile, or VoIP — the right tool differs for each

The combination of settings that makes sense for a small business owner who needs to take calls from unknown clients looks very different from what works for someone who wants to go completely dark to unsolicited contact. Your setup — and your priorities — are the piece of this that no general guide can resolve for you.