Seeing that "No Service" or "Emergency Calls Only" message on your Samsung Galaxy A55 is incredibly frustrating. You're suddenly cut off from calls, texts, and mobile data. The good news is that this is almost always a temporary glitch you can fix yourself.
I'd start with the simplest fix first, as it works more often than you'd think. Press and hold the Volume Down button and the Side button (power button) together for about 10 seconds. Keep holding them until you see the Samsung logo appear on the screen, then let go. This force restart clears out any temporary software bugs that might be blocking your signal.
Check Your Immediate Connection Status
Right after the restart, pull down the notification shade from the top of your screen twice to see the full Quick Settings panel. Make sure the Airplane Mode icon isn't highlighted. If it is, tap it once to turn it off.
While you're there, also tap the mobile data icon to turn it off, wait a few seconds, and then tap it again to turn it back on. This quick refresh can sometimes nudge the network connection back to life. If you're in a building, try stepping outside or near a window to see if your signal bars improve.
Reinsert Your SIM Card
The Galaxy A55 uses a nano-SIM card, and if it's become slightly dislodged or the contacts are dirty, it can lose connection. You'll need the SIM ejector tool that came in the box (a small paperclip works in a pinch).
Find the tiny pinhole on the top edge of the phone's frame. Gently push the tool in to pop out the SIM tray. Carefully remove the SIM card, blow on the tray slot to clear any dust, and wipe the gold contacts on the SIM with a soft, dry cloth. Reinsert the card and push the tray back in until it clicks.
Reset Your Network Settings
If the simple steps haven't worked, a network settings reset is a powerful next move. This will erase all saved Wi-Fi networks and passwords, Bluetooth pairings, and cellular network preferences, but it won't touch your photos, messages, or apps.
Go to Settings > General Management > Reset. Tap on "Reset network settings" and confirm your choice. Your phone will reboot. After it comes back on, you'll need to reconnect to Wi-Fi and Bluetooth devices, but it often resolves stubborn cellular connection problems.
Update Your Access Point Name (APN)
Your carrier's APN settings are like the phone number your A55 uses to connect to their data network. If these settings are wrong or outdated, you'll have no signal. The path is Settings > Connections > Mobile networks > Access Point Names.
You should see a list with your carrier's name. Tap the three-dot menu in the top right and select "Reset to default." If that doesn't populate the correct settings, you'll need to get the exact APN details from your carrier's website or customer service and enter them manually by tapping "Add" in that same menu.
Manually Select Your Network Operator
Sometimes your phone gets stuck trying to connect to a weak or unavailable network tower. You can force it to search for and lock onto your proper carrier. Head back to Settings > Connections > Mobile networks.
Tap on "Network operators." Your A55 will search for a moment. When the list appears, select your specific carrier (like "T-Mobile" or "Verizon") instead of leaving it on "Select automatically." Wait a minute for it to register, then switch it back to automatic. This re-registration process can clear up the issue.
Check for a Software Update
The Galaxy A55 runs on One UI 6 over Android 14. Samsung and carriers regularly release updates that fix connectivity bugs. It's worth checking to see if you're missing a patch.
Open Settings > Software update and tap "Download and install." If an update is available, connect to Wi-Fi and let it install. Your phone will restart during this process. I've seen minor updates specifically target "improved network stability," which is exactly what you need.
Use the Diagnostic Menu
Android has a hidden testing menu that lets you see the raw status of your phone's radio. Open your Phone app and dial *#*#4636#*#* exactly. This should open a "Testing" menu.
Tap "Phone information." Here, you can see your signal strength in dBm (a number closer to zero is better). You can also try tapping "Run Ping Test" or using the dropdown menu to select "LTE/GSM/WCDMA auto (PRL)" before turning the radio off and back on with the toggle.
Review Your SIM Card Status
It's possible the issue is with the SIM card itself or your account. The easiest test is to put your SIM into another compatible phone. If that phone also gets no service, the problem is with the SIM or your carrier account.
If the other phone works fine, the issue is likely with your A55. At this point, it's a good idea to contact your carrier. They can check for local network outages, ensure your account is active, and send you a replacement SIM card if needed, which often solves the problem.
Consider a Factory Reset
This is the last resort, as it will erase everything on your phone. Before you do this, ensure you have a complete backup via Samsung Cloud or Google One. If you're certain the problem is with the phone's software and not the SIM or network, you can proceed.
Go to Settings > General Management > Reset > Factory data reset. Tap "Reset" and enter your PIN if prompted. The phone will wipe itself and reboot. After setup, test the signal before restoring your apps and data, just to be sure.
