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Entering *#21# in the iPhone Phone app asks a supported mobile network for the status of unconditional call forwarding on the selected line. It is not a test for tapping, spyware, tracking, or account compromise. Whether the code works—and what appears in response—depends on the carrier and network.
What *#21# checks
The code is a supplementary-service status query. In the ETSI/3GPP command format, *# is used to interrogate a service, and service code 21 refers to unconditional call forwarding. In plain language, it asks whether the network is configured to send incoming calls to another number.
Unconditional forwarding differs from forwarding that applies only in particular circumstances. The standards describe unconditional forwarding as routing incoming calls regardless of the condition of the call recipient’s line. It concerns call handling by the mobile network, not a general inspection of the iPhone.
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|---|---|
| Unconditional | Incoming calls are forwarded regardless of the line’s termination condition. |
| Conditional | Forwarding applies only in particular circumstances, such as when a line is busy or unavailable; availability depends on carrier support. |
Why the result does not mean your iPhone is tapped
A forwarding status tells you about call routing. It does not establish that someone is listening to calls, that the phone contains spyware, or that your Apple account or carrier account has been compromised. Even an active forwarding destination is not, by itself, proof of surveillance: forwarding may have been configured intentionally or through carrier-specific services.
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An error, an unsupported response, or an unfamiliar status message also is not evidence of spying. The code’s function is narrow, and carriers do not all support the same supplementary-service commands or present results in the same way.
Check forwarding in iPhone Settings
- Open Settings > Apps > Phone > Call Forwarding.
- If you use Dual SIM, select the line you want to check.
- Review whether Call Forwarding is enabled and, if it is, inspect the displayed destination.
Apple documents this Settings route for call forwarding. Its instructions say the iPhone must be in range of the cellular network to set forwarding. Apple also notes that its documented setup requires GSM service; customers using CDMA service should contact their carrier. Conditional forwarding likewise depends on carrier support.
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- This is the latest version Telephone Call Blocker with hidden or unavailable call numbers can be blocked. And there is no fees to use it; Please keep the manual for future use.
- Block up to 4000 individual phone numbers, including incoming and outgoing calls , prefixes and up to 10 digit area codes.
- One-touch to Block: Locate a number and then press Block to add it to the blacklist.Better set the call blocker in series ( one end of it connected to your phone and another end to the PSTN telephone line); Though it can also be set up parallel, but not compatible with some phone systems.
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What to do if you find an unexpected destination
- Confirm that you checked the intended line, especially on a Dual SIM iPhone.
- If forwarding is on and you do not recognize the destination, contact your carrier through its official support channel and ask it to verify the forwarding configuration on your line.
- Use the carrier’s own instructions to change or disable forwarding. Dialing codes are not universal: for example, AT&T publishes its own activation and deactivation instructions and asks customers to wait for a confirmation tone.
Do not enter a cancellation code from an unrelated carrier’s instructions. A code that works on one network may not apply to another.
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Apple warns that unexpected links in messages, email, webpages, or apps that ask you to enable call forwarding may be scams. Do not follow a prompt you did not expect or do not recognize. If you are unsure whether forwarding was changed, check the line in Settings and ask your carrier to confirm its status.
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- Allow any blocked caller to ring through like normal with the Green Invite Button. Double Tap the Green Button to add VIP callers shown in Call History. Note: Caller ID Name and Number Service from your phone company is required for this model to work automatically.
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