Hello,
I think contacting your carrier might be the easiest way to resolve this. Out of curiosity does your carrier/location have the 5G network available?
If so, the cellular settings could need adjusting.
Use 5G with your iPhone - Apple Support
"Learn about 5G options
The default settings for 5G on iPhone are optimized for battery life and data usage based on your data plan. You can customize these options for when to use 5G and how much data to use in some apps.
Find these options by going to Settings > Cellular > Cellular Data Options. If you're using Dual SIM, go to Settings > Cellular and choose the number whose options you want to change."
If you don't have 5G or if the settings don't help, this article has steps that may work better.
If you see No Service or Searching on your iPhone or iPad - Apple Support
I hope this helps.