The fastest way depends on your phone type and what's calling you

Most phones let you block a number directly from the call log or contacts app — usually by tapping the number, finding a menu option, and selecting "block" or "block caller". On iPhone, open the Phone app, find the number in your recent calls, swipe left, and tap the block icon. On Android, open the Phone app, press and hold the number, and select "block number". This stops that specific caller from reaching you again.

If you want to block entire categories of calls — like spam, unknown numbers, or robocalls — your phone's built-in settings offer a second layer. iPhone has a "Silence Unknown Callers" toggle in Settings > Phone that sends calls from numbers not in your contacts to voicemail. Android phones vary by manufacturer, but most have a "Block unknown" or "Spam protection" setting in the Phone app's settings menu. These don't delete the calls; they just route them away from your screen.

Your phone carrier also runs its own blocking service, separate from your phone's built-in tools. Verizon offers Call Filter, AT&T offers Call Protect, and T-Mobile offers Scam Shield — all included free or for a small monthly fee. These services block calls before they reach your phone by checking incoming numbers against known spam databases. Carrier-level blocking catches more robocalls than your phone alone because it works across their entire network.

Key Takeaways

  • Block individual numbers directly from your phone's call log or contacts app in under a minute.
  • Use your phone's built-in settings to silence calls from unknown numbers or send them to voicemail automatically.
  • Your phone carrier offers free or low-cost spam blocking that catches robocalls before they reach your phone.
  • Third-party apps like RoboKiller and Nomorobo add extra filtering but require you to route calls through their service.
  • Do not answer calls from numbers you don't recognize, as answering confirms your number is active and can increase spam calls.

Blocking a single number on your phone

iPhone: Open the Phone app and go to the Recents tab. Find the number you want to block, swipe left on it, and tap the red circle with a line through it. A menu appears — tap "Block this Caller". The number is now blocked. You can also block someone from your Contacts app by opening their card, scrolling to the bottom, and tapping "Block this Caller".

Android: Open the Phone app and find the number in your call history. Press and hold the number until a menu appears. Select "Block number" or "Block contact" (wording varies by phone maker). On some Samsung phones, tap the three dots next to the number and choose "Block". The number is now blocked and will go straight to voicemail.

Once you block a number, that caller cannot reach you by phone call. Text messages from blocked numbers may still arrive on some phones — if that's a problem, you can block the number in your Messages app separately. Blocked callers do not get a notification that they are blocked; their call simply fails to connect.

Silencing calls from unknown numbers

iPhone: Go to Settings > Phone and turn on "Silence Unknown Callers". This sends any call from a number not in your Contacts, Mail, or Messages to voicemail. You will not see the call on your screen or hear a ring. The voicemail notification appears in the Phone app like normal, so you can listen later if you want. This is the simplest way to stop most spam without blocking individual numbers.

Android: Open the Phone app and tap the three-line menu (hamburger icon) in the top left. Go to Settings > Spam and abuse or Call screening (exact wording depends on your phone). Turn on "Filter spam calls" or "Spam protection". Some phones also have a "Block unknown" option that works like iPhone's Silence Unknown Callers. Unknown numbers will be blocked or sent to voicemail depending on which setting you choose.

The downside of silencing unknown callers is that legitimate calls — from your doctor's office, a delivery driver, or a business you contacted — will also go to voicemail. Check your voicemail regularly so you do not miss important calls. If you need to reach someone back, you can unblock their number temporarily or add them to your contacts.

Using your carrier's spam blocking service

Verizon Call Filter, AT&T Call Protect, and T-Mobile Scam Shield all work the same way: they check incoming calls against databases of known spam and robocall numbers before the call reaches your phone. If a number matches a spam pattern, the call is blocked or sent to a spam folder. These services are free on most plans, though some carriers offer a paid tier with extra features like reverse phone lookup.

To turn on your carrier's service, check your carrier's website or call customer service. Verizon customers can download the Call Filter app or enable it in their account online. AT&T customers can download Call Protect or enable it in the AT&T Mobile app. T-Mobile customers can turn on Scam Shield in the T-Mobile app or by calling customer service. Once enabled, the service runs automatically in the background.

Carrier-level blocking is more effective than your phone's built-in tools because it catches spam before it reaches your device. However, it is not perfect — some spam still gets through, and occasionally legitimate calls are blocked by mistake. If you miss an important call, you can check your spam folder or contact your carrier to whitelist a number.

Third-party call blocking apps

Apps like RoboKiller, Nomorobo, and Truecaller offer more aggressive spam filtering than your phone or carrier alone. They use machine learning and crowdsourced data to identify spam patterns and block calls in real time. Some apps also let you create custom block lists, set different rules for different times of day, or record calls for your records.

The trade-off is that these apps route your calls through their servers, which means they see your incoming and outgoing call data. Most reputable apps have privacy policies that explain how they use this data, but you should read them before installing. Some apps are free with ads or limited features; others charge a monthly subscription for full access.

If you use a third-party app, you may not need your carrier's blocking service — they often overlap. Check whether the app works on your phone type (some are iOS-only or Android-only) and whether it integrates with your phone's native call screen or requires you to answer calls through the app itself. Apps that require you to use their dialer are more intrusive but often more effective.

What to do if blocking does not stop the calls

Spam callers sometimes use different numbers each time they call, so blocking one number does not stop them. If you are getting repeated calls from different numbers but the same caller, enable "Silence Unknown Callers" on your phone or turn on your carrier's spam filter. Both catch calls from new numbers that match spam patterns.

If the calls are from a specific person or business that you have asked to stop calling, you may have legal options. The Telephone Consumer Protection Act (TCPA) makes it illegal for telemarketers to call you after you ask them to stop. Document the dates and times of the calls, then send a written request to stop calling to the business's address. Keep a copy for your records. If they continue calling after 30 days, you can file a complaint with the Federal Trade Commission (FTC) at reportfraud.ftc.gov or call 1-888-382-1222.

If the calls are harassing or threatening, contact your local police department and file a report. Provide the phone number, dates, times, and details of what was said. Your carrier may also be able to help — call customer service and ask about harassment or threatening calls. Some carriers can trace the source or work with law enforcement.

Why you should not answer unknown calls

Answering a call from an unknown number confirms to spam callers that your number is active and monitored by a real person. This makes your number more valuable to sell to other spam operations, which can increase the number of spam calls you receive. Even if you hang up immediately, the damage is done.

Spam callers also use a technique called "neighbor spoofing" — they call from a number that looks like it is from your area code or even your own number. This tricks you into thinking the call is local and legitimate. If you answer, they may try to scam you, steal personal information, or sell you something you do not want. The safest approach is to let unknown calls go to voicemail and call back only if you recognize the number or the voicemail sounds legitimate.

Frequently Asked Questions

Can I block text messages from the same number I blocked for calls?

Not automatically. Blocking a number in your Phone app blocks calls but may not block texts. Open your Messages app, find the conversation with that number, and look for a "Block" or "Report Spam" option. On iPhone, swipe left on the conversation; on Android, press and hold it. This blocks texts from that number separately.

What happens when a blocked caller tries to reach me?

On most phones, the call goes straight to voicemail or fails to connect. The blocked caller does not hear a message saying they are blocked — the call simply does not go through. They may think your phone is off or you are not available. Blocked callers cannot leave voicemails on most phones, though this varies by carrier and phone type.

Will blocking a number stop them from texting or emailing me?

Blocking a phone number only blocks calls and texts from that number. It does not block emails. If someone is harassing you by email, forward the message to your email provider's abuse team and mark it as spam. Most email services let you block senders or create filters that automatically delete messages from specific addresses.

Can I unblock a number if I change my mind?

Yes. On iPhone, go to Settings > Phone > Blocked Contacts and swipe left on the number you want to unblock, then tap "Unblock". On Android, open the Phone app, go to Settings > Blocked numbers, find the number, and tap the minus sign or "Unblock". The number can now call and text you again.

Do I need to pay for call blocking?

Your phone's built-in blocking tools are free. Your carrier's spam filter is usually free or costs a few dollars per month for premium features. Third-party apps vary — some are free with ads, some charge a monthly subscription (usually $3 to $10), and some offer both free and paid versions. You do not need to pay for basic blocking.