Xiaomi Internet Slow Only on Three UK Fix

Xiaomi Mobile Data Slow on Three UK – Fix

If your Xiaomi, Redmi, or POCO device has noticeably slow mobile data on Three UK, but works fine on WiFi or with other SIM cards, this guide explains why and how to fix it.

Quick Answer:
Slow mobile data on Three UK is usually caused by network congestion, 5G/4G handover issues, or signal strength. Start by switching to 4G only, toggling Airplane mode, and testing at different times and locations. Only check APN settings if data has never worked correctly or Three Support asks you to verify them.

Before Changing Your Phone Settings

If your Xiaomi is only slow on Three UK, test mobile data in a different area or at a different time of day first. If speeds improve elsewhere or late at night, the problem is usually network congestion rather than your phone.

Run a Speed Test

Get a baseline measurement before and after troubleshooting.

  1. Turn Wi-Fi off.
  2. Open Speedtest by Ookla or Fast.com.
  3. Run two or three tests to get an average.
  4. Repeat the test in another location if possible.

Why This Happens

  • Network congestion – Three UK has variable speeds depending on location and time of day, particularly in busy urban areas.
  • 5G/4G handover – Frequent switching between 4G and 5G can cause inconsistent speeds.
  • Signal strength – Weak signal directly reduces data speeds.
  • Data allowance exhaustion – If you've used all of your plan's data allowance, or your plan includes any traffic management or fair usage limits, your speeds may be reduced.
  • APN misconfiguration (less common) – Only relevant if mobile data has never worked correctly, you've recently changed settings manually, or Three Support asks you to verify them.
  • HyperOS update effect – Occasionally, a system update may affect network performance until another update is released.

Check Network Status – Three UK

Before troubleshooting your phone, check if the issue is network-wide.

  • Three network status – Check coverage and outages at three.co.uk/coverage or call 333.
  • Check local coverage – Three's coverage checker shows expected speeds in your area.
  • Test at different times – If speeds improve late at night or early morning, the issue is likely network congestion.

If outages are reported, wait for Three to resolve the issue.

Quick Fixes to Test First

Try these quick actions. Run a speed test after each step.

  1. Toggle Airplane mode – ON for 30 seconds, then OFF. Forces re-registration on Three network.
  2. Restart your Xiaomi – Full reboot clears temporary glitches.
  3. Reinsert SIM – Power off, remove SIM, check for dirt, reinsert firmly, power on.

Check Data Allowance – Three UK

If you've used all of your plan's data allowance, or your plan includes any traffic management or fair usage limits, your speeds may be reduced.

  • Check your allowance – Open the Three app or log in at three.co.uk.
  • Fair usage policy – Three applies traffic management during peak times if you exceed certain thresholds.
  • Roaming status – If you're roaming on another UK network (e.g., via Three's "Go Roam"), speeds may be restricted.

Switch to 4G Only (Temporary Test)

5G on Three can sometimes be slower than 4G due to signal strength or network configuration. Test by forcing 4G only.

  1. Settings → SIM cards & mobile networks → [Three] SIM → Preferred network type.
  2. Select 4G (LTE) only or 4G (preferred).
  3. Run a speed test.
  4. If speeds improve, keep 4G for now. If not, switch back to 5G.

Note: Some Xiaomi models hide this option. If unavailable, check Settings → Mobile networks → Preferred network type.

Reset Preferred Network Setting

Sometimes after a HyperOS update, the Preferred Network setting becomes corrupted. Resetting it can resolve inconsistent speeds.

  1. Settings → SIM cards & mobile networks → [Three] SIM → Preferred network type.
  2. Switch from current setting to the opposite (e.g., 5G to 4G). Wait one minute.
  3. Switch back to your preferred setting.
  4. Run a speed test.

Check Signal Strength

Weak signal directly affects speed. Check your signal strength:

  1. Settings → About phone → Status → SIM status → Signal strength.
  2. Good: -50 to -80 dBm. Should provide reasonable speeds.
  3. Weak: -100 to -120 dBm. Speeds will be significantly reduced.

If signal is weak, try moving to a different location or near a window. Remove any thick phone case that may block the antenna.

Compare with another phone: Check speed on another phone with a Three SIM in the same location. If both are slow, the issue is network congestion or coverage.

Check Band Priority (Advanced Information)

Three UK uses multiple frequency bands. In some locations, your phone may connect to Band 20 (800MHz), which generally provides wider coverage but may deliver lower speeds than higher-frequency bands like Band 1 (2100MHz) or Band 3 (1800MHz).

To check your current band (depending on your Xiaomi model):

  1. Open the dialler and enter *#*#4636#*#*.
  2. Tap "Phone information".
  3. Depending on your Xiaomi model, network information may include the current LTE or NR band, although this isn't available on every device.

Note: Band selection cannot typically be changed manually on Xiaomi devices without root access.

Check VoLTE (If Slow Mobile Data Only During Calls)

If slow mobile data only occurs during phone calls, temporarily disable VoLTE to see whether it makes any difference.

  1. Settings → SIM cards & mobile networks → [Three] SIM → VoLTE → OFF (temporary test).
  2. Run a speed test during a call.
  3. If speeds improve, keep VoLTE off or contact Three for provisioning support.

APN Configuration Check (Only If Mobile Data Has Never Worked Correctly)

Only check your APN if mobile data has never worked correctly, you've recently changed the settings manually, or Three Support asks you to verify them.

Verify or update your APN:

  1. Settings → SIM cards & mobile networks → [Three] SIM → Access Point Names.
  2. Select the active APN (usually labelled Three).
  3. Verify these values:
    • Name: Three
    • APN: three.co.uk
    • Username: (leave blank)
    • Password: (leave blank)
    • MMSC: http://mms.um.three.co.uk:10021/mmsc
    • MMS Proxy: mms.three.co.uk
    • MMS Port: 8799
    • APN type: default,supl,mms
    • APN protocol: IPv4/IPv6
  4. If anything differs, correct it, save, and toggle Airplane mode ON for 30 seconds then OFF.

If APN is correct but speeds are still slow: Reset APN to defaults – APN menu → three-dot menu → Reset to default. Then restart. See our Xiaomi APN Settings UK – UK Fix guide for more detail.

SIM / Network Reset Actions

Try these additional steps. Test speeds after each.

  1. Switch SIM slot – If your Xiaomi has dual SIM, move Three SIM to the other slot and test.
  2. Test SIM in another phone – If possible, test your Three SIM in another phone. If speeds are still slow, the issue is with Three or your account.

HyperOS / System Update Check

Occasionally, a HyperOS update may affect network performance until another update is released.

  • Settings → About phone → Check for updates. Install the latest available HyperOS update.
  • If the issue started after a recent update, restart your phone again and monitor if the second restart stabilises performance.

Reset Network Settings (Last Resort)

If nothing else works, reset network settings. This removes saved WiFi passwords and Bluetooth pairings.

  1. Settings → Additional settings → Backup & reset → Reset phone → Reset network settings.
  2. Confirm the reset.
  3. Restart your phone.
  4. Re-enter your Three APN settings if required.
  5. Run a speed test.

Contact Three UK

Contact Three if:

  • Slow speeds persist after completing all steps above.
  • Your SIM works fine in another phone but not in your Xiaomi.
  • You suspect a network provisioning issue with your account.
  • You're consistently getting speeds below Three's expected minimum.

How to contact Three:

  • Call Three – 333 (free from Three network) or 0333 338 1001
  • Three app – Support section
  • Three community forums – community.three.co.uk

Final Verdict

In most cases, slow mobile data on Three isn't a hardware fault. It's usually network congestion, 5G/4G handover issues, or signal strength. Start by testing at different times and locations to identify congestion. Toggle Airplane mode, then test 4G only if 5G performance seems inconsistent. Run speed tests to measure improvements. Only check APN if data has never worked correctly. Compare with another Three device if possible. If all fails, contact Three to check your account and local network status.

Frequently Asked Questions

Why is my Three mobile data so slow on Xiaomi?
Most commonly caused by network congestion, especially in urban areas during peak times. Also check 5G/4G handover and signal strength. APN issues are less common.

What APN should I use for Three UK?
The correct APN is three.co.uk. No username or password required. Only check this if data has never worked correctly.

Does Three throttle speeds on Xiaomi devices?
Three doesn't specifically throttle Xiaomi devices. If your plan includes traffic management or fair usage limits, speeds may be affected under those conditions.

Is 5G slower than 4G on Three?
In some areas, yes. Three's 5G network may have inconsistent speeds depending on coverage and band availability. Test by switching to 4G only.

Why are my Three speeds slower at certain times?
This indicates network congestion. Three's network can become overloaded during peak hours (evenings, weekends, city centres). Test at different times to confirm.

Does switching to 4G only improve Three speeds?
Often yes. 5G handover can cause inconsistent speeds. Try forcing 4G only and run a speed test.

How can I check Three coverage in my area?
Visit three.co.uk/coverage and enter your postcode. This shows expected coverage and speeds for your location.

Why is Three slower than EE or Vodafone?
Three's network architecture and frequency bands differ from EE and Vodafone. Three often has higher capacity in urban areas but may experience more congestion during peak times. Coverage and speed vary significantly by location.

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