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