You're mid-sentence, deep into a vent session with your best friend, and suddenly you realize you’ve missed three calls from your boss. No beep. No vibration. Just a string of "Missed Call" notifications that pop up like mocking ghosts the second you hang up. It’s infuriating. When call waiting not working iPhone issues crop up, it feels like your $1,000 device has forgotten how to be a phone.
Honestly, most people think it's a software bug. They restart the phone, it doesn't work, and they give up. But the reality is a bit more tangled. It’s usually a tug-of-war between your iOS settings, your carrier’s provisioning, and occasionally, the way 5G handles "slices" of data. Sometimes your phone thinks it’s doing you a favor by silencing those interruptions.
The "Invisible" Toggle That Usually Breaks Everything
Let's start with the obvious stuff that everyone misses because it's buried in the Settings app. You’d think call waiting is a universal standard, but it's actually a service that has to be "shaken hands" with by both the hardware and the network.
Go to Settings, scroll down to Phone, and tap Call Waiting.
Here is where it gets weird. Sometimes you’ll see a spinning wheel that never ends. That’s a massive red flag. It means your iPhone is trying to ask your carrier (Verizon, AT&T, T-Mobile, etc.) if the feature is turned on, and the carrier isn't answering. If the toggle is off, flip it on. If it’s already on but not working? Flip it off, wait ten seconds, and flip it back on. It sounds like "voodoo tech support," but this force-refreshes the HLR (Home Location Register) on the carrier side.
Why 5G and VoLTE Are Actually Messing With Your Calls
We were promised that 5G would change our lives. Instead, it sometimes breaks the most basic functions of a telephone.
Most modern iPhones use VoLTE (Voice over LTE) or 5G Standalone for calls. In the old days, voice calls traveled over a different "pipe" than your text messages and internet. Now, everything is data. If your cellular data connection is shaky—even if you have "full bars"—the packet of data that tells your phone "Hey, another call is coming in!" might get dropped or delayed.
If you are in a spot with spotty 5G, your iPhone might be struggling to maintain the primary call's data stream, leading it to ignore the second incoming signal entirely. You can test this by going to Settings > Cellular > Cellular Data Options and temporarily switching to LTE. If call waiting starts working again, you know your local 5G tower is having handoff issues. It's a common problem that Apple’s engineering forums have been buzzing about since the iPhone 12 launch.
Silence Junk Callers or Silence Everyone?
Apple introduced a feature called Silence Unknown Callers. It’s a godsend for avoiding spam, but it’s a blunt instrument.
If a second caller isn't in your contacts, and you have this feature enabled, your iPhone won't beep. It won't tell you they are there. It will efficiently, quietly, and ruthlessly send them straight to voicemail while you keep chatting.
Check this in Settings > Phone > Silence Unknown Callers. If it's on, that’s likely your culprit. To the person calling you, it feels like you're ignoring them. To you, it feels like your phone is broken. It’s just your iPhone being a bit too overprotective.
The Carrier Component: The Part You Can't Fix in Settings
Sometimes the problem isn't your iPhone at all. It's the "provisioning profile."
🔗 Read more: Why How to Change Time Zone on Computer Still Trips People Up
Carriers like Verizon or T-Mobile send "Carrier Settings Updates" to your phone. These are tiny files that tell your iPhone how to talk to the cell towers. If these files get corrupted—or if you recently swapped a SIM card or moved from a physical SIM to an eSIM—call waiting can get "stuck" in the off position at the network level.
You can try to force an update by going to Settings > General > About. If an update is available, a pop-up will appear after about 30 seconds. If nothing happens, you might need to do the "Nuclear Option" for networks: Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings.
Warning: This will wipe out your saved Wi-Fi passwords. It’s a pain, I know. But it’s the only way to completely flush the DNS and cellular cache that might be blocking the call waiting signal.
Digging Into Focus Modes and "Driving" Bugs
iOS 15, 16, and 17 brought us Focus Modes. They are more powerful than the old "Do Not Disturb," which means they have more ways to break things.
Check if you have a Focus mode active. Specifically, look at the Driving or Work focus. These modes can be set to activate automatically. If a Focus mode is on, it can suppress the "second call" notification UI entirely. Even if call waiting is technically "working" on the network, the iPhone UI is being told: "Do not show the user any interruptions right now."
You can verify this by swiping down from the top right to open Control Center. If a Focus icon is lit up, tap it to turn it off and try a test call.
The SIM Card Swap Reality Check
Is your SIM card five years old? If you took a SIM from an iPhone 8 and shoved it into an iPhone 15, you’re asking for trouble.
Older SIM cards weren't designed for the complex switching required by modern 5G networks. They lack the updated security keys and frequency mapping needed for seamless call management. If you’ve tried every software fix and call waiting not working iPhone is still your daily reality, go to your carrier store and ask for a fresh eSIM or a new 5G-ready physical SIM. It’s usually free, and it fixes an unbelievable amount of "ghost" issues.
Real-World Troubleshooting Steps
- Dial the Code: Open your Phone app and dial
*#43#then hit Call. This is a "star code" that queries the network directly. It will tell you if Call Waiting is enabled on the carrier's side regardless of what your Settings app says. - Toggle Airplane Mode: It's a cliché for a reason. It forces a re-registration with the local tower.
- Check Bluetooth: Weirdly, if your phone is connected to a Bluetooth headset in another room, the "beep" for call waiting might be playing in that headset while you are holding the phone to your ear. It sounds stupid, but it happens.
- Update iOS: Apple frequently releases "carrier bundle" updates inside their iOS patches. If you’re trailing three versions behind, your phone might be using an outdated protocol to talk to the tower.
Why "Call Forwarding" Is the Enemy
Check your Settings > Phone > Call Forwarding. If this is turned on, it often overrides call waiting.
In the hierarchy of phone commands, "Forward this call" usually beats "Wait for the user to answer." Some people turn on forwarding for specific business reasons and forget about it. If it’s on, the second call will never reach your device; it gets intercepted and sent elsewhere before your iPhone even knows it exists.
Practical Next Steps to Solve This Today
If you've gone through the settings and it's still failing, your first move should be the Reset Network Settings mentioned earlier. It is the most effective "soft" fix for communication errors.
If that fails, use the *43# (to enable) or #43# (to disable) dialer codes. These bypass the iPhone's graphical interface and talk directly to the cellular switching system.
💡 You might also like: Apple CarPlay iPhone 16: What Most People Get Wrong
Lastly, if the problem persists specifically when you are on Wi-Fi, turn off Wi-Fi Calling. Some routers have firewalls that block the specific SIP (Session Initiation Protocol) packets required for call waiting to function over a wireless internet connection. Disabling Wi-Fi calling forces the phone back onto the cellular radio, which is generally more stable for basic telephony features like this.
Ensure you check your "Silence Unknown Callers" setting one last time. If you are expecting calls from people not in your address book, that feature is almost certainly the wall preventing your second calls from ringing through.