Your phone can block most spam calls without you answering
Every phone — whether iPhone, Android, or older models — has built-in spam filtering you can turn on right now. The filter works by comparing incoming calls against known spam numbers and patterns, then silencing or rejecting them before they ring through. You do not need an app, a subscription, or a special service. The settings are in your phone's native call or phone app, and turning them on takes less than a minute.
Beyond the built-in filter, your phone carrier (Verizon, AT&T, T-Mobile, or whoever you pay each month) also offers spam blocking at no extra cost. Some carriers block calls automatically; others require you to turn the feature on through their website or app. A third layer — optional paid apps — exists if the first two do not catch enough, but most people find the combination of phone settings plus carrier filtering sufficient.
Key Takeaways
- iPhones have a "Silence Unknown Callers" setting that sends calls from numbers not in your contacts straight to voicemail.
- Android phones have a "Block Unknown" or "Filter Unknown Calls" setting in the Phone app that does the same thing.
- Your carrier (Verizon, AT&T, T-Mobile, etc.) offers free spam blocking that you may need to turn on through their website or app.
- Calls from known spam numbers are blocked before they reach your phone, while calls from unknown numbers can be silenced to voicemail.
- If spam still gets through after using both phone and carrier filters, third-party apps like Nomorobo or RoboKiller can add another layer.
How to block spam on iPhone
Open Settings, then tap Phone. Scroll down and turn on "Silence Unknown Callers." This sends any call from a number not in your contacts, recent calls, or messages straight to voicemail. You will not see a notification, and the call will not ring through. Legitimate callers you know will still reach you normally.
If you want to see which calls were silenced, open the Phone app, tap Recents, and look for calls marked "Silenced Notifications." You can call them back or add them to your contacts if they are legitimate.
For additional filtering, check your carrier's app. Verizon offers Call Filter (free version blocks known spam; paid version adds more features). AT&T offers Call Protect. T-Mobile offers Scam Shield. Open your carrier's app or website and turn on the free tier if it is not already active.
How to block spam on Android
Open the Phone app (the one you use to make calls), tap the three-line menu icon, and go to Settings. Look for "Block Unknown" or "Filter Unknown Calls" — the exact name varies by phone maker and Android version. Turn it on. Unknown numbers will be sent to voicemail or blocked outright depending on your phone model.
Some Android phones also have a "Spam Protection" or "Call Screen" setting in the same menu. Turn that on as well if it appears. This catches calls from numbers flagged as spam by Google or your carrier.
Next, open your carrier's app. Verizon Call Filter, AT&T Call Protect, and T-Mobile Scam Shield all have free versions. Download your carrier's app from the Google Play Store, sign in, and enable spam blocking if it is not already on.
What your carrier's spam filter does differently
Your phone's built-in filter silences unknown callers. Your carrier's filter identifies specific numbers known to be spam and blocks them before they reach your phone at all. The two work together: the carrier catches the worst offenders, and your phone's unknown caller filter handles the rest.
Carrier filters update constantly as new spam numbers are reported. You do not have to do anything once you turn them on. The filtering happens on the carrier's network, not on your phone, so it works even if your phone is old or has limited storage.
Some carriers block these calls silently (you see nothing), while others send them to a spam folder you can review later. Check your carrier's app settings to see which option is active and change it if you prefer the other.
When to use a third-party spam blocking app
If spam calls still reach you after turning on your phone's unknown caller filter and your carrier's spam blocking, a third-party app can add another layer. Popular options include Nomorobo, RoboKiller, and Truecaller. These apps use larger databases of known spam numbers and can block calls more aggressively than carrier filters.
Most third-party apps are free but offer paid versions with extra features like call recording, detailed spam reports, or blocking by category (robocalls, telemarketers, etc.). The free versions are usually enough. Download from your phone's app store, grant the app permission to access your calls, and turn on blocking in the app's settings.
One drawback: third-party apps run on your phone rather than on the carrier's network, so they use more battery. If your phone's battery drains quickly, stick with the built-in and carrier filters instead.
How to report a spam call so it gets blocked for others
When you receive a spam call, you can report it directly in your phone's call log. On iPhone, swipe left on the call in Recents and tap "Report as Junk." On Android, long-press the call and tap "Report as Spam" or "Block Number." Your report goes to Apple, Google, or your carrier, and that number gets added to the spam database used by other users.
If a call is particularly aggressive or threatening, you can also report it to the Federal Trade Commission at reportfraud.ftc.gov. The FTC does not stop individual calls, but it tracks patterns and can take action against large-scale spam operations.
What to do if spam calls keep getting through
If you are still receiving spam calls after enabling all available filters, the calls may be coming from spoofed numbers — fake caller IDs that change with each call. These are harder to block because the number is different every time. In this case, consider not answering calls from unknown numbers at all, or ask your carrier if they offer a more aggressive blocking tier (some carriers have paid options that block more calls).
You can also add your number to the National Do Not Call Registry at donotcall.gov. This does not stop all spam, but it reduces calls from legitimate telemarketers. Scammers ignore the registry, so it is less effective against robocalls and fraud attempts.
If a specific number keeps calling, block it manually: on iPhone, tap the call in Recents and select "Block This Caller"; on Android, long-press the call and tap "Block Number." Blocked numbers go straight to voicemail and you will not see notifications from them.
Frequently Asked Questions
Will I miss important calls if I silence unknown callers?
Legitimate callers you know will still reach you normally. If someone new needs to reach you, they can leave a voicemail, and you will see it in your voicemail app. You can call them back if it is important. If you are expecting a call from a specific unknown number (like a doctor's office), you can temporarily turn off the filter or add that number to your contacts beforehand.
Can I block calls from a specific number?
Yes. On iPhone, open the Phone app, find the number in Recents, swipe left, and tap "Block This Caller." On Android, long-press the number and tap "Block Number." That number will go straight to voicemail. You can unblock it anytime by going back to the same menu and selecting "Unblock."
Do I need to pay for spam blocking?
No. Your phone's built-in filter and your carrier's free spam blocking are sufficient for most people. Paid apps and paid carrier tiers exist, but they are optional. Start with the free options and only upgrade if spam is still a major problem after a few weeks.
What is the difference between blocking and silencing calls?
Silencing sends calls to voicemail without ringing your phone. Blocking does the same thing but may also prevent the caller from leaving a voicemail, depending on your settings. Both keep the call from interrupting you. You can review silenced or blocked calls later in your voicemail or call log.
Will blocking spam calls affect my ability to receive legitimate calls?
No. Spam filters only block numbers flagged as spam or calls from unknown numbers (if you have that setting on). Calls from people in your contacts, recent calls, or messages will always come through normally. If a legitimate caller is blocked by mistake, you can unblock them and add them to your contacts so they reach you in the future.