Why a blocked number is dialed on Xiaomi: the complete guide

When a blocked subscriber suddenly breaks through the digital security of your smartphone, it is puzzling and alarming. Xiaomi and Redmi users often find that the blacklisted number keeps making calls and the phone rings as if nothing had happened. This is not a mysticism or a matrix failure, but a completely understandable technical phenomenon associated with the peculiarities of the Android operating system and the MIUI shell.

The lock mechanism in modern smartphones is not as straightforward as in older push-button phones. When a call comes in, the system first receives an incoming connection signal, identifies the number, and then checks it against a database of prohibited contacts. In this short period of time, you can hear a beep or see a notification before the system automatically resets the call. The delay between the call signal and the software reset is 0.5 to 2 seconds, which is sometimes perceived by the user as a full call.

There are also a number of third-party factors that can bypass standard restrictions. Operators use different voice protocols, and some of them can mask the true source of the call. In this article, we will take a closer look at why this happens, how Xiaomi’s lock algorithms work, and what steps need to be taken to ensure complete silence.

Technical features of the blocker in MIUI

The MIUI shell, which is installed on Xiaomi, Redmi and POCO smartphones, has its own powerful security module that is integrated deep into the system. Unlike standard Android, where locking often depends on the OS version and the processor manufacturer, Xiaomi solutions work at the level of system services. However, even such advanced protection has its own vulnerabilities related to process priority. The system must first “hear” the call to understand that it needs to be blocked.

The incoming call processing algorithm is as follows: modem receives a signal -> the system determines a number -> check by the blacklist base -> action (reset or pass), the problem arises if the database check takes longer than waiting for the connection, or if the priority of the call process is higher than the priority of the filtering process, in which case you will hear a short horn.

⚠️ Note: If you hear a beep, but the screen does not light up and the phone does not vibrate, then the lock worked normally, but the operator managed to transmit the signal to start the connection before the reset.

It is important to understand the difference between software locking on a device and operator-side locking. The blacklist in MIUI only works when the phone is on and in the network area. If the device is off or in flight mode, locking cannot be done locally. It is also worth noting that some system services may have exclusive rights to ignore user filtering settings.

Reasons for blocking bypass: hidden numbers and service codes

One of the most common reasons a locked number still rings is because it uses a hidden ID technology, so a caller can use a service code or a phone setting to hide their number, and for your phone, it looks like an Unknown Number or a Hidden Number, and if the blacklist settings don't tick off all unknowns, the call will pass.

And then there are service short numbers that are used by banks, delivery services, and government agencies, and often they change their masks or use a pool of different identifiers. Even if you blocked one particular number that you were called from yesterday, today the call may come from a nearby number from the same database, and the system will miss it because it is not yet blacklisted.

• 📞 Hidden ID: The subscriber uses the code before dialing (e.g. #31# on some networks), which hides the number from the definition.
• 🔄 Shift. CID: Call centers use a dynamic change of number determinant, so locking one contact does not help.
• 🌐 VoLTE and Wi-Fi Calling: When calling over Internet protocols, the signal may come in a different way, and a standard filterer MIUI It may not be able to be processed instantly.

Also worth mentioning is Viber, WhatsApp, and other messengers: If a person is locked in a phone book, it doesn't always mean that apps are automatically blocked. The privacy settings in each app need to be adjusted separately. Xiaomi has a blacklist synchronization feature, but it doesn't work with all apps by default.

Setting up a blacklist in Xiaomi and Redmi smartphones

To minimize the likelihood of unwanted calls, you need to configure the built-in blocker correctly. In MIUI, this functionality is hidden in the Security app. This is where all the key switches that control which calls will pass and which will not. It is not enough to just add a number to contacts marked "block", you need to configure global rules.

Go to the Security app, then select Antispam (or Blacklist). Here you will see a list of blocked numbers and settings. It is important to check whether the hidden number lock is activated. To do this, click on the gear icon or menu in the upper right corner and select Lock Settings.

You'll find some important options in the lock settings menu. The first is Keyword Block. This is a unique feature of Xiaomi that allows you to block SMS with certain text, but for calls, the option to "Block all unknown numbers" is more important. If you turn on this feature, any number that is not in your phone book will automatically be reset. This is a radical but effective method.

Don't forget to check your notification settings, too. If you want to know who tried to reach you, leave the blocking notifications on, otherwise you won't see the call log history, although they will remain in the anti-spam logs.

The impact of telecom operators on the display of calls

Often the problem is not the phone, but the specifics of the mobile operator. GSM, 3G and 4G/LTE networks transmit incoming calls in different ways. In some cases, the operator can transmit a packet of data about the subscriber number with a delay. Xiaomi phone receives the command “Incoming call”, emits a sound, and only after a split second comes the packet “Identifier: +7999...”. If by this time the blacklist has already passed (or failed due to the lack of a number at the start of the call), the connection is established.

There is also the concept of forwarding: If you have ever set up a forwarding on your number or it was activated by the operator (for example, when it is unavailable), the call can come as a repeated or altered call, which the system perceives as a new communication session, and previous attempts to block.

⚠️ Warning: Some operators use whitelist technology for their service numbers, which means that calls from rescue services, police or the operator themselves can force their way through any network-level locks and the phone must let them through.

Another factor is roaming. If you're roaming, the call routing goes through the partner networks, in which case the number data can be distorted or come in a non-standard format, which confuses the MIUI algorithms, and the call goes as "unknown" or "local."

Third-party applications and program conflicts

Users often install additional number and spam-blocking apps, such as Truecaller, GetContact or Kaspersky Who Calls. Conflict between Xiaomi's built-in blocker and a third-party app is a common cause of crashes. When a call arrives, both apps try to intercept call control. If the third-party app is slower or has a lower priority, the built-in system may miss the call before the external blocker says "Stop."

In addition, newer versions of Android (especially 10, 11, 12 and above) have significantly restricted the rights of apps to work with telephony in the background, which is done for security, but it has led to the fact that third-party blockers are no longer as effective as before.

• 📉 Priority conflict: Two apps try to reset the challenge at the same time, creating a process race.
• 🔋 Energy saving: System MIUI It can “sleep” the background process of the blocker, and it will not work in time.
• 📜 Outdated databases: If the spammer database is not updated, the new number will be filtered.

The solution could be to abandon third-party solutions in favor of Xiaomi’s built-in tools, which have system rights and are not subject to power saving restrictions to the same extent. Or, on the contrary, completely disabling the built-in filter and using only one powerful external application, which is given all the necessary permissions in the Apps → Permissions → Phone menu.

Solving the problem: step-by-step instructions

If you still have blocked numbers, you need to do a complete setup review. Don't rely on "checkmarks somewhere." Go through the following algorithm to rule out software errors and human error.

First, clear the cache of the Phone and Antispam app. The accumulated temporary files can cause errors in the blacklisted database. Go to Settings → Apps → All apps → Antispam (or Security) and select Clear → Clear cache. Do the same for the Phone app.

The way to reset call settings:


Settings → Applications → Application Management → Phone → Settings Reset (if available)




Or through the engineering menu: ##4636## → Phone Information → Refresh/Reset (with caution)

Next, check if the problem number is added to the Favorites or the White List. There is a hierarchy in MIUI: if the number is in the contacts and is marked as important, it can ignore the blacklist rules. Make sure that the number is removed from the contacts completely, and then added specifically to the blacklist through the Antispam menu.

⚠️ Note: When clearing the Phone or Antispam app data, your blacklist may be deleted. Take screenshots of important locked numbers in advance or export them if such a feature is available in your version MIUI.

If nothing works, try to put your phone in Do Not Disturb mode with the "Let Only the Favourites" setting, which is a system lock layer that covers everyone else, and in this mode, the phone will be silent for everyone except those you explicitly allowed.

Frequently Asked Questions (FAQ)