Have you checked your handset is compatible with iD Mobile VoLTE (4G Calling), @Josephward?

https://www.idmobile.co.uk/help-and-advice/approved-handsets 

I changed my phone to be compatible with 4G.

Hopefully your new phone is on the iD approved for VoLTE list, @Josephward. 

It is.

I have just been talking to Harry Wilson of ID customer care. He was able to sort my problem, by sending me a new SIM card. To obtain my new SIM card he asked for my bank details, even though he said he had all my details. I had given him my name, address and date of birth, to verify that I was the account holder. As I was not comfortable giving my bank details over the phone to a complete stranger, he said he could not send the new SIM card to me without my bank details and therefore I am in the same position of not being able to make or receive calls. Is the only solution to leave ID?

No just change SIM at any CURRYS store; your phone may be a 4g one, but may not have VOLTE capability;

Hi @Josephward 

When you say ‘I was not comfortable giving my bank details over the phone to a complete stranger’ where did you get the contact phone number from? I ask this as iD Mobile DO NOT have a customer services phone line as the only way to chat with them is via Live-Chat
https://www.idmobile.co.uk/live-chat

Good job you didn’t give your bank details as iD Mobile would NEVER ask you for these details!

You have to be able to connect to LTE to connect to the VoLTE network and to be able to make/receive calls. Even if you move to another provider you may still have the same problem if LTE is not provisioned on your handset.
What phone make/model do you have? 
This info will definitely help someone point you in the right direction.

Thanks, be careful if you are private messaged from this site, I was lucky to avoid being scammed!!!!

Going back to Currys for advice.