Built-in blocking tools work for most unwanted calls

Every smartphone has a native call-blocking feature built into the phone itself. On iPhone, open the Phone app, find the number in your recent calls or voicemail, tap the info icon (circle with an i), scroll down, and tap "Block this Caller." On Android, open the Phone app, long-press the number, and select "Block number." These blocked numbers cannot reach you by call or text — the call goes straight to voicemail, and you receive no notification.

This method works when ready and requires no app read or subscription. The blocked number stays blocked until you manually unblock it. You can view your block list in iPhone Settings under Phone > Blocked Contacts, or in Android under Phone > Settings > Blocked Numbers. If you block a contact by accident, you can unblock them the same way.

The limitation of built-in blocking is that it only stops calls from numbers you already know. It does not filter spam calls from unknown numbers or calls that spoof real numbers. For that, you need a second layer.

Key Takeaways

  • Your phone's built-in block feature stops calls from specific numbers you already know, and works when ready without any app or cost.
  • Carrier-level filtering through AT&T Call Protect, Verizon Call Filter, or T-Mobile Scam Shield blocks spam and robocalls before they reach your phone.
  • Third-party apps like RoboKiller and Nomorobo add extra filtering layers and can block calls based on patterns rather than just known numbers.
  • Do not answer calls from unknown numbers, do not press buttons when a robocall asks you to, and do not give personal information to callers you did not initiate contact with.

Carrier filtering stops spam before it reaches you

Your mobile carrier offers a filtering service that catches spam and robocalls before they ring your phone. AT&T Call Protect (free basic version, $3.99/month for advanced), Verizon Call Filter (free basic version, $2.99/month for advanced), and T-Mobile Scam Shield (free) all work the same way: they analyze incoming calls against known spam databases and block or label them as likely spam.

To turn on carrier filtering, contact your carrier directly or check your carrier's website. AT&T customers can enable Call Protect through the AT&T mobile app or by calling 611. Verizon customers can set up Call Filter in the My Verizon app. T-Mobile customers can turn on Scam Shield in the T-Mobile app. Once enabled, spam calls are blocked automatically, and you see a "Spam Risk" label on calls that pass through but match spam patterns.

The free versions of these services block the most common robocalls and spam. The paid versions add features like the ability to block calls from numbers not in your contacts, see who is calling before you answer, and get detailed reports. For most people, the free version is sufficient.

Third-party apps add a second filtering layer

RoboKiller and Nomorobo are the two most widely used third-party call-blocking apps. Both work by analyzing call patterns and comparing incoming numbers to databases of known spam sources. RoboKiller costs $3.99/month or $39.99/year and blocks calls, texts, and voicemails. Nomorobo is free for basic blocking and $1.99/month for advanced features like call recording and detailed logs.

These apps are most useful if your carrier's free filtering is not catching enough spam, or if you want features the carrier service does not offer. RoboKiller, for example, can answer robocalls with a recorded message that wastes the caller's time and marks your number as unresponsive. Nomorobo integrates with your phone's native contacts so blocked calls do not appear in your recent calls list at all.

The trade-off is that third-party apps require you to grant them permission to access your call history and contacts. Read the privacy policy before installing. Both RoboKiller and Nomorobo are available on iPhone and Android through the App Store and Google Play.

How to block calls from spoofed numbers

Spoofed calls use technology to display a fake number on your caller ID — often a number that looks like it is from your own area code or a government agency. You cannot block a spoofed number the way you block a real one, because the same spoofed number rarely calls twice. Carrier filtering and third-party apps are more effective against spoofing because they recognize the calling pattern rather than the displayed number.

If you receive a spoofed call claiming to be from your bank, the IRS, or another institution, hang up when ready. Do not press any buttons the call asks you to press. Call the institution directly using the number on your statement or their official website to verify whether they actually called you. Real banks and government agencies do not call asking for passwords, Social Security numbers, or payment information.

You can report spoofed calls to the Federal Trade Commission at reportfraud.ftc.gov. The FTC uses these reports to identify patterns and pursue the people behind the calls.

Do not answer calls from unknown numbers

The simplest way to avoid unwanted calls is to not answer them. If a call is important, the caller will leave a voicemail. Legitimate businesses and government agencies do not expect you to answer on the first try. If you do answer an unknown call and realize it is spam, hang up when ready. Do not press any numbers, do not say anything, and do not stay on the line to argue with the caller.

Answering a spam call or pressing a button tells the caller your number is active and monitored. This makes your number more valuable to spam operations and increases the frequency of calls. Staying silent or saying "yes" to confirm your number is the same as confirming it is a working number.

If you are expecting a call from an unknown number — a doctor's office, a delivery service, a job interviewer — you can answer it. For all other calls, let voicemail catch it. Most legitimate callers will leave a message.

Manage your contact information to reduce spam

Spam callers buy phone numbers from data brokers, websites that collect and sell personal information. You cannot stop this entirely, but you can reduce how many lists your number appears on. Do not post your phone number on social media, do not enter it into online forms unless necessary, and do not give it to businesses that do not need it.

If you have already received a lot of spam, your number is already on multiple lists. Blocking individual numbers or using filtering will reduce the calls you receive, but the calls may not stop completely. Changing your phone number is an option if the spam is severe, though it is disruptive and your new number may eventually end up on spam lists too.

You can register your number with the National Do Not Call Registry at donotcall.gov. This does not stop all calls — political organizations, charities, and companies you have done business with are exempt — but it does reduce calls from telemarketers. Registration is free and permanent.

When to contact your carrier or law enforcement

If you receive repeated calls from the same number making threats, asking for money, or claiming you owe a debt you do not owe, contact your carrier's customer service and ask them to investigate. Carriers can sometimes trace calls and take action against the source. Document the dates and times of the calls and what was said.

If the calls are threatening or harassing, you can file a police report. Provide the police with the phone number, the dates and times of the calls, and a description of what was said. The police may not be able to stop the calls when ready, but a report creates a record that can help if the harassment escalates.

If you believe you are the target of a scam — for example, someone is impersonating you or your business — report it to the FTC at reportfraud.ftc.gov and to your state's attorney general's office. These agencies track scams and can pursue legal action against the people running them.

Frequently Asked Questions

Will the person I block know that I blocked them?

No. When you block someone on your phone, they do not receive a notification. Their calls go to voicemail, and they will not know whether you blocked them, ignored the call, or did not see it. They may suspect it if they never get a response, but your phone does not tell them.

Can I block calls from a specific area code?

Not with your phone's built-in tools. Some third-party apps like RoboKiller allow you to block entire area codes, but this is risky because legitimate calls from that area code will also be blocked. Carrier filtering is a better option because it blocks spam from any area code without blocking legitimate calls.

What should I do if I accidentally answer a spam call?

Hang up when ready. Do not press any buttons, do not say anything, and do not stay on the line. Hanging up tells the caller nothing about your number. If the same number calls again, block it using your phone's built-in block feature.

Do I need to pay for call blocking?

No. Your phone's built-in blocking is free, and your carrier's basic filtering is free. Paid apps and paid carrier upgrades add features, but you do not need them to block most unwanted calls. Start with the free tools and upgrade only if they are not catching enough spam.

Can robocalls spoof my own phone number?

Yes. Robocalls can display any number on your caller ID, including your own. If you receive a call from your own number, it is definitely spam. Do not answer it, and do not call the number back. Block it and move on.