Block unknown numbers directly in your phone settings

Most phones have a built-in setting to silence calls from numbers not in your contacts. On an iPhone, go to Settings > Phone > Silence Unknown Callers and toggle it on. On Android, the process varies by manufacturer — Samsung phones have Settings > Call > Call Rejection > Auto Reject List, while Google Pixel phones use Settings > Apps & Notifications > Notifications > Advanced > Default Notification Settings, then Phone app settings.

When you enable this feature, unknown callers hear a ring but your phone stays silent. The call goes to voicemail, and you can see it in your call log later. This is different from blocking — the caller isn't told they're blocked, and you still have a record of the attempt.

The trade-off is that legitimate callers you don't know — a doctor's office, a delivery driver, a potential employer — will also go to voicemail. You'll need to check your voicemail regularly to catch important calls.

Key Takeaways

  • Your phone's native settings can silence unknown callers without blocking them, sending calls directly to voicemail instead.
  • Third-party apps like TrueCaller, RoboKiller, and Nomorobo offer spam detection and blocking but require you to grant access to your call logs and contacts.
  • Blocking a specific number (one you already know) is faster than setting up unknown call filtering and works the same way on both iPhone and Android.
  • Your phone carrier may offer spam filtering at no extra cost — AT&T Call Protect, Verizon Call Filter, and T-Mobile Scam Shield are built into many plans.
  • No method catches all spam, and some legitimate callers will be blocked no matter what you choose.

Use your carrier's spam filtering service

AT&T, Verizon, and T-Mobile all offer spam and robocall filtering built into their networks. AT&T Call Protect is free on most plans and blocks calls flagged as spam before they reach you. Verizon Call Filter works the same way. T-Mobile Scam Shield is included with most T-Mobile accounts and flags suspected scam calls with a warning label.

These services work at the network level, meaning they filter calls before your phone even rings. You don't need to install anything or change settings — the filtering happens automatically. You can usually see which calls were blocked in your call history, marked as spam or scam.

The limitation is that carrier filtering relies on databases of known spam numbers. New numbers or spoofed numbers (calls that fake a real phone number) often slip through. If you're getting calls from the same number repeatedly, blocking it directly on your phone is more reliable.

Block specific numbers you already know

If a particular number keeps calling you, blocking it takes seconds. On iPhone, open the Phone app, find the number in your recent calls or voicemail, tap the info icon, and select Block This Caller. On Android, open the Phone app, long-press the number, and tap Block Number.

Once blocked, that number cannot reach you — calls go straight to voicemail and you won't see notifications. The caller won't know they're blocked; they'll just hear a ring and eventually reach voicemail. You can unblock the number anytime by reversing the same steps.

This method works well for harassment or unwanted calls from people you recognize. It doesn't help with random unknown numbers, since you'd have to block each one individually as it calls.

Consider a third-party call-blocking app

Apps like TrueCaller, RoboKiller, and Nomorobo use databases of known spam numbers and machine learning to identify likely spam calls. TrueCaller shows caller identity for unknown numbers and lets you block entire categories (like "suspected spam" or "telemarketing"). RoboKiller uses audio fingerprinting to detect robocalls. Nomorobo focuses on blocking robocalls and lets you report new spam numbers.

These apps require permission to access your call logs, contacts, and sometimes your location. They also require you to set them as your default phone app or give them permission to intercept calls. Read the privacy policy before installing — some apps sell anonymized call data to third parties, while others keep it private.

Third-party apps often catch more spam than carrier filtering alone, but they're not perfect. They can also block legitimate calls if the number matches a spam pattern. If you use one, check your blocked calls occasionally to make sure nothing important was filtered.

Understand what gets blocked and what doesn't

No blocking method catches everything. Robocalls that spoof real phone numbers (making it look like a call is coming from a local number or a business you know) are hard to detect because the number itself isn't inherently spam. A call from "555-0100" might be a scammer one day and a legitimate business the next.

Spoofed calls are the reason why blocking by number alone doesn't solve the problem. If a scammer calls from a spoofed number and you block it, they straightforward call from a different spoofed number tomorrow. This is why filtering services that look at call patterns and metadata are more effective than straightforward number blocking.

Legitimate callers sometimes get caught by spam filters. A doctor's office calling from a shared line, a delivery service using an automated system, or a survey company can all trigger spam detection. If you're expecting a call from an organization, you may want to temporarily disable unknown call silencing or check your voicemail more frequently.

Reduce calls by limiting who has your number

Blocking and filtering work best as a second line of defense. The first line is controlling who gets your number in the first place. When you sign up for online services, use a privacy-focused email address instead of giving your phone number. When a business asks for your number, ask if it's required or optional.

Your number can also be harvested from public sources — old websites, data breaches, or sold by data brokers. You can request removal from some data broker lists through sites like OptOutPrescreen.com (for credit offers) or by contacting brokers directly, though this is time-consuming and not always effective.

If you're getting a high volume of spam calls, changing your number is sometimes faster than trying to block them all. This is a last resort, but it works — your new number won't be in spam databases yet.

Report spam and robocalls to help others

When you block a spam call, you can report it to your carrier or to the FTC. On iPhone, you can report a number as spam directly from the call log. On Android, the Phone app has a Report Spam option. These reports help carriers and apps improve their spam detection.

You can also file a complaint with the Federal Trade Commission at ReportFraud.ftc.gov. The FTC doesn't investigate individual complaints, but patterns of complaints help them identify large-scale scams and take action against the people running them.

If you're getting calls about a specific scam (like a fake IRS call or a tech support scam), reporting it helps warn others who might fall for the same scheme.

Frequently Asked Questions

Will the person know I blocked them?

No. When you block a number, the caller hears a normal ring and eventually reaches your voicemail. They won't receive a message saying they're blocked. Some apps that block calls before they ring might behave differently — check your app's documentation.

Can I block calls from my own area code?

You can block individual numbers from your area code, but you can't block all calls from a specific area code on most phones. If you're getting many calls from numbers in your area code, a third-party app with pattern detection may work better than blocking individual numbers.

What's the difference between blocking and silencing unknown callers?

Silencing sends calls to voicemail without blocking — you can still see the call in your history and call the person back if you want. Blocking prevents the call from reaching you at all and usually removes it from your call log. Silencing is gentler if you're worried about missing legitimate calls.

Do I need to pay for call blocking?

Your carrier's basic spam filtering is usually free. Third-party apps vary — some are free with ads, some charge a monthly fee (usually $3 to $5), and some offer a free version with limited features. Check your carrier first before paying for an app.

What should I do if a blocked number keeps calling from different numbers?

This is a sign of organized spam or harassment. If it's harassment, document the calls and consider reporting to local police. If it's spam, enable unknown call silencing or use a third-party app that detects patterns rather than blocking individual numbers. Changing your number may be necessary if the harassment is severe.