Call Waiting Not Working on iPhone: Troubleshooting

When call waiting fails on an iPhone, a second incoming call may go straight to voicemail, give the caller a busy signal, or never appear on screen while you are already talking. In most cases the cause is a setting, a carrier-side feature or a call filter, not broken hardware. The steps below move from narrowing down the cause to reversible fixes, then to confirming the result.

Identify the symptom and environment

Before changing anything, write down exactly what happens to the second call and under which conditions. Record:

• What the second caller experiences: a busy tone, ringing with no answer, or your voicemail greeting.
• Whether a missed-call notification appears on your iPhone afterward.
• What type of call you were already on: a regular cellular call, a Wi-Fi Calling call, or an audio or video call in an app such as FaceTime or a messaging app.
• Whether it affects every caller or only unknown numbers or specific contacts.
• Which number is involved, if your iPhone uses two lines with Dual SIM or eSIM.
• Whether call audio was playing through the earpiece, the speaker, Bluetooth headphones or a car system.
• Your iOS version (Settings > General > About) and your carrier.

These details matter because call waiting for ordinary phone calls is a carrier service. The iPhone switch only asks the network to turn it on or off. Calls made through apps are handled by each app, so the iPhone Call Waiting setting may not describe their behavior.

Isolate where the fault occurs

Use your notes to decide which of these areas is the likely source:

• Carrier provisioning: if the Call Waiting switch is on but second calls still never alert you, the feature may not be active on your plan or may behave differently with your current calling mode.
• Forwarding: if Call Forwarding is on, or your carrier has a forward-when-busy rule (sometimes created when voicemail is set up), a second call is diverted before it can wait.
• Filters: Do Not Disturb or another Focus, Silence Unknown Callers, blocked contacts and call-blocking apps can send calls to voicemail. If only some callers are affected, check these first.
• Dual SIM: when you are on a call on one line, calls to the other line typically go to voicemail. Apple describes an exception that depends on carrier support for Wi-Fi Calling and the Allow Cellular Data Switching option; check Apple's current Dual SIM guidance for your model.
• Audio route: the waiting alert plays where the call audio is going, so with headphones or a car system you may only hear it there, or miss it. Testing with the earpiece removes this variable.
• Wi-Fi Calling: some carriers handle a second call differently over Wi-Fi Calling than over the cellular network, so comparing both modes can point to the network side.

A practical test needs two other phones or two helpers: one calls you, and while you are on that call, the second one calls. Repeat it once with Wi-Fi Calling on and once with it off, holding the iPhone to your ear without headphones. Note the result each time.

Try reversible fixes in order

Menu locations differ by iOS version. On iOS 18 and later, Phone options are under Settings > Apps > Phone; on earlier versions they are under Settings > Phone. If a label does not match your device, type it into the search field at the top of Settings. Test after each step so you know which change made the difference.

• Check the switch: open the Phone settings and tap Call Waiting. It should be on. If it spins for a long time or turns itself off, the iPhone could not confirm the setting with the carrier; note this for later. Turn it off, wait a moment and turn it back on.
• Check forwarding: in the same Phone settings, open Call Forwarding and turn it off unless you use it intentionally.
• Remove filters temporarily: turn off any active Focus from Control Center, turn off Silence Unknown Callers in Phone settings, review your blocked contacts, and switch off call-blocking apps under Call Blocking and Identification in Phone settings.
• Re-register with the network: turn Airplane Mode on, wait a few seconds and turn it off, or restart the iPhone.
• Update: open Settings > General > About; if a carrier settings update is available, a prompt appears there. Install pending iOS updates from Settings > General > Software Update.
• Compare calling modes: turn Wi-Fi Calling off (found under Phone or Cellular settings, depending on version) and repeat the test.
• Carrier codes, only if your carrier confirms them: on many GSM networks, dialing *43# enables call waiting and *#43# shows its status. These are network codes rather than iPhone features, and not every carrier supports them.
• Reset network settings as the last local step: on recent versions it is under Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings. It removes saved Wi-Fi networks and passwords and other network configuration, so read the confirmation text and make sure you can re-enter your Wi-Fi details before proceeding.

Confirm the result

Repeat the exact test that failed, using the same line, calling mode and audio route. A working setup shows the second caller on screen during the first call, plays an alert tone, and offers options to hold, end or decline (labels vary by iOS version). Ask the second caller whether they heard ringing rather than your voicemail greeting. Then restore the settings you changed one at a time, such as Wi-Fi Calling, your Focus schedule and call-blocking apps, and test after each. This shows which setting interfered and lets you keep the protections you rely on instead of leaving them off.

If the problem remains

Keep a short record before contacting support, since it saves repeated troubleshooting:

• iOS version, carrier and plan, and which line was tested.
• Whether the Call Waiting switch stays on or shows a spinner or error.
• Results with Wi-Fi Calling on and off, and with filters removed.
• What the second caller heard, with the dates and times of the tests.
• If you can try it, whether the same SIM behaves the same way in another phone.

Contact your carrier first and ask them to confirm that call waiting is active on your number, that no forward-when-busy rule is set on their side, and that the feature is supported with your calling mode. If the carrier confirms the account is correct and the fault follows the iPhone rather than the SIM, contact Apple Support with your notes. A call waiting failure on its own is not proof of a hardware fault; it is most often an account, network or settings issue.