HI ​@Sally Haywood 

I do apologise that your SIM is not working on your original handset.

Please make sure your SIM tray is not damaged. 

What to try (in order)
1. Clean and reseat the SIM

• This fixes more issues than you’d expect:

• Power off phone

• Remove SIM

• Gently wipe gold contacts

• Blow out the SIM tray slot

• Reinsert firmly

• Reboot

2. Reset Network Settings (this often fixes the “turns on then off” behaviour)

On Android:

Settings → System → Reset → Reset Wi-Fi, Mobile & Bluetooth

On iPhone:

Settings → General → Transfer or Reset → Reset → Reset Network Settings

(This does NOT delete your data.)

3. Manually select your network

Turn off automatic network selection:

Go to Mobile Networks → Network Operators → Search manually

Choose your UK carrier
If the phone can’t register, you’ll know immediately.

4. Update carrier settings

   On iPhone:
   Settings → General → About → wait for “Carrier Settings Update” prompt
   On Android:
   Settings → About Phone → Software Update → Carrier configuration

5. Clear the Phone app & SIM toolkit cache (Android only)

   Settings → Apps → Show system apps →

   Phone Services / SIM Toolkit / Carrier Services
   → Storage → Clear Cache + Clear Data

6. Check if the phone’s IMEI is blocked or corrupted

   Dial:
   *#06#

   If IMEI = null, 0, or corrupted → network won’t allow registration.

   If IMEI is fine → move on.

-Owethu

​@Sally Haywood Since your sim card is working in other mobile phone's without issue I would say the fault is with your handset.

Have you tested your husband's sim card in your phone or any other sim card in your phone?

Joe 🙂

Yes, my husband put his sim (also iD) in my phone and it worked but that wasn’t much good to me. So, my sim works in other phones and another sim works in my phone but my sim doesn’t work in my phone!

​@Sally Haywood  I know it's not much good to you, but it was to eliminate your phone.

Login to you account and request a replacement sim card or go to a Curry's store with ID passport of driving licence as the staff won't service you without proof of identity. 

Seem your sim card has a touch of the winter blues and a replacement may solve your problem here.

Joe

I know this is an old Post but I have exactly the same Issue as Sally,  My wife had an ID mobile Sim that worked fine in her Oppo f11 Pro Phone but refused to work when we came back to the UK, we went to Curry’s and they put in a new Sim, said it would be fine but it did not work, I tried the sim in my Mate20 Phone and it was fine, I put my Talk Mobile sim in her phone and worked fine. I tried her Sim in my old Sony Ericson nope nothing... My Talk mobile sim worked with every phone.. So I gave up,  I already had a Labara Sim in my old Sony Ericsson phone I put it my wife's phone and that works fine, we use very little data so the cheapest for a fiver is ok. Must be something with ID Mobile Network that rejects certain phones, her phone was purchased in the Philippines a few years ago but has never had a problem with any other Sim  it worked before we went on holiday, very strange. ID Mobile problem I’m sure

Hi ​@EstelaMarie 

Could you please try a mobile network reset and also check your APN settings, as this may help resolve the issue you are experiencing with your SIM card.

1) Reset Network Settings (Oppo F11 Pro)
This often resolves most signal and data issues.

Open Settings
Tap Additional Settings (or System & Device, depending on your ColorOS version)
Go to Back up and reset
Select Reset phone / Reset options
Tap Reset network settings
Confirm by selecting Reset Settings

This will reset Wi-Fi networks, mobile data settings, and Bluetooth connections. Once completed, please restart your phone.

2) APN Settings (Manual Setup)
If the issue persists, please set up the APN manually:

Go to:
Settings → SIM & Mobile Network → Access Point Names (APN) → Add New APN

Enter the following:

Internet APN

Name: iD Mobile
APN: id
Username: (leave blank)
Password: (leave blank)
MCC: 234
MNC: 20
APN type: default
APN protocol: IPv4

MMS Settings (for picture messages)

MMSC: http://mms.um.idmobile.co.uk:10021/mmsc
MMS proxy: mms.idmobile.co.uk
MMS port: 8799
APN type: default,supl,mms

Once entered:

Save the APN
Select it as active
Restart your phone again

Please let us know if the issue continues after these steps.

-Michael Z