Why is only my regular calling not working
Why has this happened a second time, how do prevent it
Question marked as
Top-ranking reply
Optimize the range of the mobile network, see this Apple article:
If you see No Service or Searching on your iPhone or iPad
If you see No Service or Searching on your iPhone or iPad - Apple Support
If it doesn't help contact your carrier, maybe the SIM card is damaged, ask for a replaced (new) card. Normally it is free.
Check if the SIM tray is bent, as even a tiny misalignment can cause the SIM card to not fully connect with the internal contacts in your iPhone.