The error “Unidentified Subscriber” (sometimes shown as “Unidentified subscriber” or “Unidentified user”) means your phone’s SIM card or number is not recognized by the network for SMS delivery.
Let’s break down what this means, why it happens, and how to fix it.
⚙️ What “Unidentified Subscriber” Really Means
This error comes directly from the SMSC (Short Message Service Center) or HLR (Home Location Register) in your carrier’s network. It indicates:
The subscriber ID (IMSI) tied to your SIM is not known or provisioned in the network’s database.
The network cannot map your phone number to an active subscriber record.
It’s typically a carrier or SIM provisioning issue, not a phone issue.
In short: the network doesn’t know who you are, so it can’t route your SMS.
Common Causes
| Cause | Description |
|---|---|
| Deactivated SIM | The SIM card or phone number has been deactivated (for inactivity, non-payment, or porting). |
| SIM not provisioned for SMS | The carrier hasn’t properly linked SMS capability to your account. |
| Faulty or corrupted SIM | The SIM chip can no longer correctly report your IMSI to the network. |
| Network migration or update | Occasionally happens during backend updates on the carrier’s system. |
| Incorrect SMSC configuration | Your SMSC (service center number) is missing or incorrect. |
Step-by-Step Fix
1. Restart and Reregister
Turn your phone off and on again.
This forces it to re-register with the network.
Check if you see your carrier name and signal bars.
2. Check the SIM in Another Phone
If the same message appears, the issue is with your SIM or account.
If it works in another phone, the issue might be with your device’s SIM slot or software.
3. Verify SMSC (Service Center Number)
Every carrier has an SMSC number responsible for routing SMS.
Go to your Messaging app settings → SMSC or Message Center number.
Make sure it matches your carrier’s correct number (I can provide it if you tell me your country and carrier).
If blank or incorrect, update it and restart your device.
4. Check for Account Suspension or Porting Delays
If your line was recently ported (moved from another network) or inactive, the SMS function might not be reactivated yet.
Contact your provider and ask them to refresh your SMS provisioning or re-register your IMSI.
5. Request SIM Replacement
If your SIM is old, damaged, or not LTE/VoLTE-capable:
Visit a service center and request a replacement SIM with the same number.
This reissues your IMSI in the HLR and usually resolves the error instantly.
Optional Diagnostic Codes (for Android)
You can check the network registration manually:
Dial
*#*#4636#*#*→ choose Phone informationCheck IMS Registration Status and SMSC number.
If “Not Registered” or SMSC is blank, that’s confirmation of the issue.
When to Contact Your Carrier
If all the above fail, call your carrier’s technical support and say:
“I’m getting an ‘Unidentified Subscriber’ error when sending SMS. Please check if my IMSI is correctly provisioned for SMS in the HLR and if my number is active.”
They can usually fix it remotely by:
Re-provisioning your SIM
Refreshing HLR/VLR registration
Assigning the correct SMSC routing