Firewall: Robo Call Blocker review: The app equivalent of Kryptonite against iPhone robocalls

Block robocalls, spam calls, and telemarketers from ringing through to your iPhone.

firewall robocall blocker hero
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At a Glance

According to The New York Times, upwards of 48 billion Americans were hounded by robocalls in 2018, an increase of 56.8 percent over the previous year. That averages out to roughly 150 scam, telemarketing, and unwanted calls annually for every adult with a phone—a number expected to balloon higher in the future.

That’s precisely why a cottage industry flourishes on the App Store, supplying tools to combat this menace. Unfortunately, most call blocker solutions rely on outdated, ineffective blacklists, or worse yet, require users to do the heavy lifting by reporting rogue numbers as they pop up. A new app called Firewall takes the opposite approach: Whitelisting everyone you know and sending the rest to limbo.

firewall in call experience 2 up IDG

Firewall mimics the iPhone in-call experience, with an option to reroute VoIP calls to your cellular carrier at the tap of a button.

While that may sound like dropping a nuke on your backyard to get rid of a few pesky bugs, Firewall did a remarkable job of eliminating nuisance calls on my iPhone X. In recent months I’ve received a handful of daily intrusions, but after installing Firewall, they were entirely eliminated.

The app accomplishes this feat by forwarding incoming cellular (but not FaceTime) calls to the company’s servers, where unknown numbers are vetted against multiple known spam databases. Anything that survives this first line of defense is then matched against a whitelist of your device contacts, with everyone else going to built-in voicemail.

firewall whitelist Ad Hoc Labs

During setup, Firewall adds your device contacts to a whitelist, and others can be manually added at any time.

When active, Firewall emulates the look and feel of a traditional iPhone in-call experience. The app bypasses carrier-based voicemail, transcribing recorded audio with a far higher degree of accuracy than iOS or Google Voice—so good in fact, that you can understand every voicemail just by reading, rather than listening. Should a blocked caller turn out to be someone you know using a different number, they can be added to the whitelist in a couple taps.

A few caveats

Remarkable as Firewall is snuffing out solicitors, there are a few limitations worth noting. For starters, the app currently only works in the U.S. with AT&T, Sprint, T-Mobile, and Verizon. Intercepted calls are redirected to your iPhone using VoIP, which consumes cellular or Wi-Fi data rather than plan minutes.

You can get around this by tapping the on-screen “switch to cell” option, which reroutes the call-in progress to the cellular network. It’s a little clunky but comes in handy while on unreliable wireless connections.

firewall call detail Ad Hoc Labs

Blocked calls from unrecognized numbers can easily be added to your Firewall whitelist so they won’t be ignored in the future.

Also, you can customize what’s spoken during voicemail greetings for whitelisted and blocked calls, but there’s no way to record outgoing messages in your own voice.

Although contacts remain on your device at all times, the idea of forwarding incoming calls may give some users pause. For me, the satisfaction of purging robocalls was ultimately worth it. Firewall did miss a call from one of my contacts, but infrequent outages are routed to voicemail, with a push notification reminder to check recent calls.

Bottom line

Firewall is Kryptonite for unwanted calls and easily worth the modestly-priced monthly subscription for a little peace and quiet, assuming you don’t mind entrusting incoming calls to a third-party app.

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At a Glance
  • From the makers of the Burner app, Firewall blocks robocalls, spam calls, and telemarketers from ringing through to your iPhone using voicemail transcription and a whitelist created from device contacts.


    • Completely eliminate unwanted incoming calls on iPhone
    • Built-in voicemail with fast, super-accurate transcription
    • Option to switch current call to carrier network


    • Occasionally missed whitelisted calls routed straight to voicemail
    • Requires forwarding incoming calls using VoIP
    • Currently limited to U.S. carriers only (AT&T, Sprint, T-Mobile, Verizon)
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