Welcome to the Community Forum--I'm sorry to hear that you are having network availability problems. Apologies as well for the delay in getting back to you about this.
Checking into this, I can see that you will need to give us a call about this issue. Just ring 150 (free from a Virgin Media landline & Virgin Media mobile) or 0345 454 1111 (from any other phone).
Need help changing SIM card? Find out more about activating your 4G ready SIM. 4G SIM Swap Help