Don't hold your breath while waiting for a solution to this. I have had the same problem, along with a 'Refreshing sim data' message for about at least a year. I have had 2 new sim cards, the second one having been delivered today. I used to have no problem with wifi calling, however a year or so ago the fault started.
Let me run this past you...
Inside my flat I cannot make/receive calls without being connected to wifi calling, nor can I send or receive texts.
As I said, today, sat in my flat without wifi calling, and the occasional 'Refreshing sim data' message for company, I opened the envelope and looked at the instructions for activating my "shiny new sim card". The instructions were that I send a certain text to Virgin to let them know that I was ready to change sim cards. Then, once I had inserted the "shiny new sim card" I was to text a code number to Virgin. I would receive a text in reply to confirm that the card had been activated. If I didn't receive such a message, I was to send the code anyway and wait up to 24 hours for a confirmatory text message.
Can anyone else see a possible flaw in this plan?
As footnote, I again checked my hpone while I was out and about earlier today. The wifi calling feature was active (although I was nowhere near any wifi, and as is normal I could call or text anyone. Back in the flat - not signal.
Virgin have told me several times now that I need a new handset, however when I see so many people with the same wifi calling or refreshing sin data messages, I am reluctant to spend money to only find that the problem still exists.
(For information, I have taken my phone to a phone repair shop twice in the past year and they have found nothing wrong with it.)