Perhaps the iPhone is network locked, ​@Joey2806. 

Whereabouts did you purchase the iPhone? 

I am having a nightmare with same issue.  Says NO SIM.  I am now without any data or call facillities and live agents are useless

got it from o2 over 2 years ago ​@andewhite, didn’t think phones were locked nowadays, got the PAC code to change over the number from o2 and was hoping it would work but no success

You can check if the iPhone is locked, ​@Joey2806. 

Try Settings > General > About, then scroll down to Network Provider Lock. 
If unlocked to any network, it should say “No SIM Restrictions”. 

Checked Network Provider Lock and says No SIM Restrictions, guessing there must be an issue with the SIM card then

Okay ​@Joey2806, earlier you said the iD SIM worked in a Samsung phone - is that still the case?

Premature ejecting would be my guess

When a SIM is inserted into a phone certain hand shakes have to take place. The SIM has to check the phone, the phone has to check the SIM, the manufacturer of the phone checks both and our service providers do the same. Some configurations* go back and forth and only then does the SIM and phone get on. So if you whip it out too soon and stick it in another phone the SIM ain’t got a clue what’s going on and neither would the service provider as they log more than you think.

*provisioning, setting WiFi calling, enabling 5GHz as the default for hotspotting, checking the phone ain’t nicked, and so on.

Hello ​@Joey2806 

Thanks for getting in touch. 

We are sorry for the initial issues with the service but we are happy to hear this is now working for you. 

​@LJ111 Are you still experiencing issues? 

Thanks, 

Nat