Spam calls are a universal nuisance, but your Xiaomi 15 running HyperOS 2 has several built-in tools to fight back. You can block specific numbers, enable system-wide filters, and even use Google's services to screen suspicious calls before they ever ring.
Block a Number from Your Call Log
Open the Phone app and tap the Recents tab. Find the unwanted number in your list and tap on it to view the call details. On the details screen, you'll see a Block option. Tap it, confirm your choice, and that number will no longer be able to reach you with calls or SMS.
Block a Contact Directly
If the spammer is already in your contacts, open the Contacts app and select their entry. Tap the More button (three dots) at the top right and choose Block numbers from the menu. This will block all phone numbers associated with that contact card.
Use the Built-in Harassment Filter
Xiaomi's HyperOS includes a proactive harassment filter. Go to Settings > Apps > Manage apps > Phone > Caller ID and spam. Here, you can toggle on See caller ID and spam and Filter spam calls. With this enabled, calls identified as spam may be flagged or silently blocked.
You can also report numbers directly from here to help improve the filter. I've found this feature gets more effective over time as it learns from user reports.
Block All Unknown Callers
For the most aggressive approach, you can block any number not in your address book. Navigate to Phone app > Settings (three-dot menu) > Blocked numbers. At the top of this screen, toggle on Block calls from unknown numbers.
Be aware this will block calls from doctors' offices, delivery drivers, or any other legitimate caller not saved in your phone. They can still leave a voicemail, which you'll receive a notification for.
Manage Your Block List
To review or unblock numbers, go to the same Blocked numbers menu within the Phone app's settings. You'll see a complete list of every number you've manually blocked. Tap the X or trash icon next to any entry to remove it from the block list.
Leverage Google's Phone Services
If you use Google's Phone app as your default, it offers excellent spam protection. Open the Google Phone app, go to its Settings > Caller ID and spam. Enable both See caller ID and spam and Filter spam calls.
For an even stronger defense, enable Call Screen in the same menu. When an unknown or suspected spam call comes in, you can tap "Screen call" to have Google Assistant answer and transcribe the caller's reason for calling in real-time, letting you decide if it's worth picking up.
Block Spam Text Messages
Open the Messages app and find a text from the number you want to block. Tap and hold the conversation, then tap the three-dot menu and select Details. On the contact details screen, tap Block & report spam. This blocks the number and reports the message to help improve spam filters.
Consider a Third-Party App
For a database-powered solution, apps like Truecaller can be installed from the Google Play Store. These apps use crowdsourced data to identify and block spam calls from millions of numbers globally. After installation, you'll need to grant it permissions to manage calls and contacts.
Be mindful of privacy policies with these apps, as they often upload your contact list to their servers to function. It's a trade-off between convenience and data sharing.
What Actually Happens to Blocked Calls
When you block a number on your Xiaomi 15, the caller is typically redirected to voicemail after one ring, or they may hear a busy signal. They won't receive any specific notification that they've been blocked. Text messages from blocked numbers are deleted automatically and never appear in your inbox.
Remember, you can always force restart your phone if you experience any HyperOS UI glitches while adjusting these settings by holding the Power button for about 15 seconds until it reboots.