The basic methods depend on what your phone company offers
Most landline providers offer call blocking as part of their service, though the exact steps and features vary by company. The three main routes are: using your phone's built-in blocking feature (if your phone has one), calling your phone company to add a number to a block list, or using a third-party device that sits between your phone line and your handset. Which one works for you depends on your phone model, your provider, and whether you want to block one number or many.
The fastest option is usually your phone itself. Many modern landline phones — particularly cordless models and phones with digital displays — have a "block" or "reject" button you can press after a call comes in. Some let you enter numbers directly into a blocked list through the phone's menu. If your phone doesn't have this feature, your phone company almost certainly does, and you can set it up with a single call.
Key Takeaways
- Check your phone's manual or display menu first — many landline phones have a built-in block feature that works without calling your provider.
- If your phone has no blocking feature, call your phone company and ask for their call blocking service, which usually costs nothing or a few dollars per month.
- When you call your provider, have the exact phone number ready and ask whether they block the number when ready or if there is a delay.
- Third-party devices like call screeners sit between your phone line and handset and can block numbers without involving your provider, though they require a power outlet.
- Blocking one number is different from blocking categories of calls (like unknown numbers or robocalls), which may require a separate service or device.
Using your phone's built-in block feature
If your landline phone has a digital display and a menu button, it likely has call blocking built in. After an unwanted call comes in, look for a "block," "reject," or "do not disturb" option on the phone's screen or in its menu. Some phones let you press a dedicated button; others require you to navigate through settings. Check your phone's manual or look on the back of the handset for a model number, then search online for "[model number] how to block calls" to find the exact steps.
Once you block a number this way, that phone will reject future calls from that number — the call will not ring through. Some phones let you view a list of blocked numbers and unblock them if you change your mind. The advantage is that blocking happens when ready and costs nothing. The disadvantage is that it only works on that specific phone; if you have multiple handsets on the same line, you would need to block the number on each one separately.
Asking your phone company to block the number
If your phone has no blocking feature, or if you want the block to explore to all phones on your line, call your landline provider's customer service number (it is on your bill). Tell them you want to block a specific phone number and provide the full number, including the area code. Ask them three things: whether the block is free or costs extra, whether it takes effect when ready or after a delay, and whether they can block multiple numbers or just one.
Most major providers — including Verizon, AT&T, CenturyLink, and regional carriers — offer call blocking at no extra cost or for a small monthly fee (usually $3 to $5). The block typically takes effect within a few hours to a day. When the blocked number calls, the caller will either hear a message saying the number is not in service, or the call will straightforward not ring through on your end. Some providers let you manage your block list online through your account; others require you to call back to add or remove numbers.
Using a third-party call-blocking device
If you want to block calls without involving your phone company, or if your provider does not offer blocking, you can use a standalone device that plugs between your phone line and your handset. These devices — sometimes called call screeners or call blockers — filter incoming calls and prevent blocked numbers from ringing through. Popular models include the CPF3000 (made by Clarity) and devices sold under the Nomorobo brand, though many others exist.
These devices work by intercepting the incoming call signal before it reaches your phone. You enter the numbers you want to block into the device's memory, and it compares each incoming call against that list. Most can block between 50 and 1,500 numbers depending on the model. The main advantage is independence from your provider; the main disadvantage is that the device needs to be plugged in and powered on at all times, and it takes up space near your phone jack. Prices range from $30 to $100 depending on features.
The difference between blocking one number and blocking categories
Blocking a single phone number is straightforward: you tell your phone, your provider, or a device to reject calls from that specific number. Blocking categories — such as all unknown numbers, all calls from outside your area code, or all robocalls — is a different service and may not be available through the same method.
Some phone companies offer robocall filtering as a separate service (often free or low-cost), and some third-party devices specialize in filtering robocalls rather than letting you block individual numbers. If you are dealing with repeated robocalls rather than a specific harassing number, ask your provider whether they offer robocall filtering. If you are blocking a specific number, the methods described above will work.
What happens after you block a number
When you block a number, the caller's experience depends on your method. If your phone company is doing the blocking, the caller usually hears a message saying the number is not in service or that the call cannot be completed. If you are using your phone's built-in feature or a third-party device, the call may straightforward not ring through on your end, and the caller may hear a busy signal or no answer.
In all cases, you will not see the call on your phone or in any call log. The blocked number cannot leave a voicemail (if you have voicemail service). If you change your mind and want to unblock the number, the process is the reverse: press unblock on your phone, call your provider to remove it from their list, or delete it from your device's memory.
Frequently Asked Questions
Can I block a number if I do not know who it is?
Yes. You do not need to know the caller's identity to block their number. If you have the phone number (from your caller ID or a missed call log), you can block it. If you do not have the number, you can ask your provider whether they offer call filtering for unknown numbers, which is a different service from blocking a specific number.
Will the person I block know that I blocked them?
No. The caller will hear a message or busy signal, but they will not receive a notification that you specifically blocked them. They may assume your line is busy or out of service. There is no way for them to know whether you blocked them or whether your phone is straightforward not available.
Can I block a number temporarily and then unblock it later?
Yes. Whether you use your phone's feature, your provider's service, or a third-party device, you can unblock a number at any time by reversing the process. On your phone, this usually means finding the blocked number in a list and pressing unblock. With your provider, call customer service and ask them to remove the number from your block list.
What if the same person calls from different numbers?
You will need to block each number separately. If someone is harassing you from multiple numbers, contact your local police non-emergency line or your phone company's abuse department. Some providers can investigate patterns of harassment and take action beyond blocking individual numbers.
Does call blocking work on all landline phones?
Not all phones have built-in blocking, but all landline providers can block numbers on your behalf. If your phone is older or very basic, it may not have a menu or display screen, which means you cannot block directly on the phone. In that case, your provider's blocking service is your best option.