The fastest way to block telemarketers depends on your phone type

On an iPhone, open the Phone app, find the telemarketer's 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." Both phones let you block numbers one at a time this way, but neither method stops new numbers from the same company from reaching you.

If you want to reduce telemarketer calls before they reach you, your phone carrier offers free tools. Verizon customers can turn on "Call Filter" in the My Verizon app. AT&T offers "Call Protect" through the AT&T Mobile app. T-Mobile includes "Scam Shield" at no cost. These tools use databases of known telemarketer and spam numbers to block or flag calls automatically. They are not perfect — some legitimate calls get caught, and new telemarketer numbers slip through — but they catch the majority of unwanted calls.

Key Takeaways

  • Your phone's built-in block feature stops one number at a time, but your carrier's free spam-blocking tool (Call Filter, Call Protect, or Scam Shield) blocks entire categories of telemarketer calls automatically.
  • The National Do Not Call Registry stops most telemarketing calls, but it takes up to 31 days to work and does not cover charities, political organizations, or companies you have done business with recently.
  • Third-party apps like RoboKiller and Nomorobo add extra filtering on top of your carrier's tool, but they cost money and require you to route calls through their system.
  • If a telemarketer calls after you registered with the Do Not Call Registry, you can file a complaint with the FTC, though enforcement is slow and most callers are overseas.

Register with the National Do Not Call Registry

The National Do Not Call Registry is a free list maintained by the Federal Trade Commission (FTC). When you add your number to it, telemarketers are legally required to stop calling you within 31 days. You can register at donotcall.gov or by calling 1-888-382-1222 from the phone you want to protect.

The registry does not cover all calls. Charities, political organizations, surveys, and companies you have done business with in the past 18 months can still call you. Debt collectors and banks can call regardless of the registry. If you recently gave your number to a company — even to check a balance or ask a question — they may call you for up to 18 months after that contact.

Once you register, keep the confirmation number. If a telemarketer calls after 31 days, you can file a complaint at donotcall.gov and reference that number. The FTC investigates patterns of violations, but individual enforcement is slow. Most telemarketer calls come from overseas, where U.S. law is hard to enforce.

Use your carrier's spam-blocking tool

Your phone company already offers free spam and telemarketer blocking. These tools work differently than the Do Not Call Registry — they do not rely on you reporting numbers. Instead, they use databases of known telemarketer patterns and numbers to block or flag calls before they reach you.

Verizon's Call Filter is available through the My Verizon app. AT&T's Call Protect is in the AT&T Mobile app. T-Mobile's Scam Shield is built into T-Mobile phones and available through the T-Mobile app. All three are free. You turn them on, and they run in the background. Some calls will be blocked outright; others will be flagged as "Spam Risk" or "Scam Likely" so you can decide whether to answer.

These tools are not perfect. They sometimes block legitimate calls from doctors' offices or delivery services that use shared phone systems. They also miss new telemarketer numbers that have not yet been added to their databases. But they catch the bulk of unwanted calls without requiring you to do anything after setup.

Block individual numbers on your phone

When a telemarketer calls and you want to block that specific number, use your phone's built-in block feature. On iPhone, go to Phone > Recents, find the number, tap the info icon (the "i" in a circle), scroll down, and tap "Block this Caller." On Android, open the Phone app, long-press the number in your call history, and tap "Block number."

This method works immediately — that number will not call you again. But it only blocks the one number. Telemarketing companies often use multiple numbers, sometimes changing them daily, so blocking one number does not stop the company from reaching you with a different one. Use this method for numbers that call repeatedly, but combine it with your carrier's spam-blocking tool for broader protection.

Consider a third-party call-blocking app

Apps like RoboKiller, Nomorobo, and Truecaller add extra filtering on top of your phone's built-in tools and your carrier's spam blocker. RoboKiller uses artificial intelligence to identify telemarketer patterns. Nomorobo maintains a crowdsourced list of spam numbers. Truecaller identifies callers by matching incoming numbers against a global database.

These apps cost money — RoboKiller is roughly $4 per month, Nomorobo is $2 per month, and Truecaller has a free version with limited features and a paid version at roughly $5 per month. Most require you to route calls through their system, which means they see your incoming calls. If privacy is a concern, read their privacy policy before installing.

You do not need a third-party app if your carrier's tool is working well. But if you still receive many telemarketer calls after setting up Call Filter, Call Protect, or Scam Shield, a paid app may catch what your carrier misses. Start with your carrier's free tool first.

What to do if a telemarketer ignores the Do Not Call Registry

If a telemarketer calls after your number has been on the Do Not Call Registry for more than 31 days, you can file a complaint. Go to donotcall.gov, click "File a Complaint," and enter the phone number that called you, the date and time of the call, and the company name if you know it. You can also file by calling 1-888-382-1222.

The FTC uses complaints to identify companies that repeatedly violate the registry. If a company gets many complaints, the FTC may investigate and pursue legal action. However, individual complaints rarely result in immediate action. Most telemarketer calls come from overseas call centers or spoofed numbers, making enforcement difficult. The registry works best as a preventive tool — most legitimate U.S. companies do respect it.

Frequently Asked Questions

Will blocking a number stop the telemarketer from calling with a different number?

No. Blocking one number only stops that specific number from reaching you. Telemarketing companies often use multiple numbers, sometimes rotating them daily. Your carrier's spam-blocking tool (Call Filter, Call Protect, or Scam Shield) is more effective because it identifies telemarketer patterns rather than individual numbers.

How long does the Do Not Call Registry take to work?

Up to 31 days. Telemarketers are required to stop calling within that window after you register. If calls continue after 31 days, the company is violating the law and you can file a complaint with the FTC.

Can telemarketers call me if I have done business with them recently?

Yes. The Do Not Call Registry does not cover companies you have done business with in the past 18 months. If you called a bank, visited a store, or made a purchase, that company can call you for 18 months even if you are on the registry. You can ask them to remove your number from their list directly.

Do I need to pay for call blocking?

No. Your phone's built-in block feature is free, the Do Not Call Registry is free, and your carrier's spam-blocking tool (Call Filter, Call Protect, or Scam Shield) is free. Third-party apps like RoboKiller cost money but are optional if your carrier's tool is working well.

What if the telemarketer is spoofing a local number?

Spoofed numbers are harder to block because the number changes with each call. Your carrier's spam-blocking tool catches many spoofed calls by identifying telemarketer patterns rather than relying on the number itself. If spoofed calls continue, a paid third-party app may help, but the most reliable defense is not answering calls from numbers you do not recognize.