Getting a "Call Failed" message on your OnePlus Open can stop you in your tracks, especially when you're trying to connect with someone. This usually means your phone is having trouble communicating with your carrier's network. It's often a quick fix related to your signal, a software hiccup, or a simple setting.
Let's start with the fastest solution, which often clears things up in seconds.
Toggle Airplane Mode On and Off
The quickest way to reset your cellular connection is by using Airplane Mode. This forces your phone to disconnect from the network and reconnect fresh, which can clear out temporary glitches.
Swipe down from the top of your screen to open the Quick Settings panel. Tap the Airplane Mode icon to turn it on, wait about 10 seconds, then tap it again to turn it off. You should see your signal bars disappear and then come back.
Check Your Signal Strength
Weak signal is the most common culprit for failed calls. Look at the signal indicator in the top-right corner of your status bar. If you only have one or two bars, try moving to a different location.
Sometimes, just stepping near a window or going outside can make a big difference. If you're indoors in a large building, the structure itself might be blocking the signal.
Perform a Force Restart
A simple reboot can fix a surprising number of software-related issues. For the OnePlus Open, press and hold the Power button for about 10 seconds, or until you feel it vibrate and see the OnePlus logo appear on the screen.
This is different from a normal restart and can clear out deeper system processes that might be interfering with the phone app or network services.
Verify Your Do Not Disturb and Focus Settings
Check that your calls aren't being silently blocked by a system setting. Swipe down from the top and look for a moon icon or a "Silent" mode indicator in the status bar.
You can also go into Settings > Sound & vibration > Do Not Disturb to make sure no rules are active that would prevent calls from coming through. OxygenOS's Focus modes work similarly.
Ensure Automatic Date and Time is Enabled
Incorrect system time can sometimes cause authentication issues with cellular networks. It's an easy thing to check and fix.
Open Settings > Additional settings > Date & time. Make sure the switch for "Use network-provided time" is turned on. This lets your carrier sync the correct time automatically.
Check Your Blocked Numbers List
It's worth a quick look to make sure you haven't accidentally blocked the number you're trying to reach. This would result in an immediate call failure.
Go to your Phone app, tap the three-dot menu in the top-right, and select Settings > Blocked numbers. If the number is there, you can tap the 'X' next to it to unblock.
Confirm Cellular Data and Roaming Settings
Make sure your mobile data is actually enabled. Go to Settings > Mobile network. Ensure the "Mobile data" toggle is switched on.
If you're traveling, you might need to enable data roaming. In the same Mobile network menu, tap "SIM 1" or "SIM 2" (whichever you're using for the call), and then turn on the "Data roaming" option.
Update Your Carrier Settings
Your carrier occasionally sends small configuration updates to improve network connectivity. These can happen automatically, but it's good to check.
Connect to a Wi-Fi network first. Then, go to Settings > About device > SIM status. Sometimes an update prompt will appear here if one is available from your provider.
Try Switching Network Modes
Sometimes the 5G or 4G LTE connection in your area might be unstable for voice calls. You can try forcing your phone to use an older, but often more reliable, network type.
Go to Settings > Mobile network. Tap on your active SIM card, then tap "Preferred network type." Select "3G/2G (auto)" instead of "5G/4G/3G/2G (auto)." Test your call, then switch it back afterward.
Inspect and Reseat Your SIM Card
A loose, dirty, or faulty SIM card is a classic cause of call failures. The SIM tray on the OnePlus Open is located on the left side of the frame.
Use the ejector tool that came in the box (or a small paperclip) to pop out the tray. Remove the SIM card, gently wipe the gold contacts with a soft cloth, and carefully reinsert it. Make sure it's seated completely flat in the tray before pushing it back into the phone.
Update Your OxygenOS Software
Software updates frequently include patches for bugs that can affect calling, network stability, and the phone app itself. It's always a good step if you're having persistent issues.
Plug in your 67W SUPERVOOC charger to ensure you have plenty of battery. Go to Settings > About device > OxygenOS version and tap "Check for update." Download and install any available updates.
Reset Your Network Settings
This is a more thorough step that will wipe all your saved Wi-Fi networks, Bluetooth pairings, and cellular settings back to default. It won't delete your personal data like photos or messages.
Go to Settings > Additional settings > Backup & reset > Reset phone > Reset network settings. Tap to confirm, and your phone will reboot. Afterward, you'll need to reconnect to Wi-Fi and re-pair Bluetooth devices.
Contact Your Mobile Carrier
If you've tried everything here and calls are still failing, the problem likely lies with your carrier's service. There could be a temporary network outage in your area, a problem with your account, or your SIM card might need to be replaced.
Give their customer service a call from another phone if possible. They can check for outages, reprovision your line on their network, or send you a new SIM card.
