How to block spam calls and unwanted numbers

Mark Vogel profile image September 23, 2025 | 3 min read

There’s nothing more annoying than being bombarded with phone calls from unknown numbers, answering them and realizing it was nothing but spam and a waste of time. Trust us, we know, we’ve even experimented with answering every spam call possible (spoiler: we do not recommend doing this).

So, how do you block numbers? There are a number of ways that we’ll get to, but it’s first important to understand how it works.

What is call blocking?

In the simplest terms, call blocking is when your telephone provider stops a caller from reaching your number. What happens when someone calls a number they’re blocked from varies based on the service. For some, the call could go straight to voicemail. For others, they might hear a message saying their call will not be connected. Or they could just hear some kind of indefinite tone, like a sort of purgatory.

What about call spoofing?

Call spoofing, which is when a caller uses a fake number or Caller ID name to get you to pick up the phone, is a more modern way for scammers to trick the systems put in place to reduce unwanted calls.

Learn more: US Cities Ranked by Spam Calls per Capita

It’s often difficult to block spoofed calls, just because the number being shown is not necessarily the number that’s calling, but it’s always best to take a beat and consider the phone number and Caller ID name before answering. The government, your bank and other services you’re signed up for are unlikely to call you. They are more likely to send you physical mail or an alert through an app or text message instead.

How do you block spam calls?

Now that you have some basic background, we can talk about how to block numbers. Yes, even how to block robocallers.

Here’s how to use call blocking in Ooma Office:

  1. Head to the administrator portal and choose Settings.
  2. Click System and then choose Call Blocking.
  3. Finally, select Block Anonymous calls and Play a Busy Signal.

You’ve enabled Call Blocking with Ooma Office, but you can also go a step further.

If you have Ooma Office Pro, you can take advantage of Ooma Office’s integration with Nomorobo’s suspected scammer lists to block even more numbers in bulk.

The setup is the same as regular Call Blocking, but you will also get to choose how you deal with scammer calls: indefinite ring, straight to voicemail or busy tone.

Because scammers never rest, you can also add numbers to the call blocking list either one by one or in bulk.

To add a single number, head back over to the Call Blocking section of the System section of the Settings page.

Type in the number you want to block and add it to the list. You’re done!

You can also add numbers to the block list from the call log list by clicking the little circle with a slash through it.

If you have an Apple Numbers, Google Sheets or Excel file with a bunch of numbers you want to block, you can upload those to the call blocking list too.

In the System section of Settings, choose Call Blocking. Then select Bulk Actions and click Import Block List CSV. Choose your file and whether you want it to replace your block list or add to it. Ooma will validate the file and let you know if there are any errors. Make sure the column headings are in the top row and the list is saved as a CSV file.

So how do you block spam calls? You have all the tools you need! Just keep in mind that it’s a bit of a cat and mouse game, and that scammers never stop trying to circumvent the restrictions around phone calls. Services like Ooma Office or Ooma Office Pro can make blocking spam calls easier.

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