Why my phone keep on telling me that I can’t make or receive any calls and messages please?

Go through the various suggestions in the support article below but if they don't help, and your network carrier can't help, then  contact Apple Support for further investigation.

Support article: If you see No Service or Searching on your iPhone or iPad - Apple Support

Or if service is established but you still cannot text or call

Set up imessage and facetime:-

Settings, Messages, Turn off iMessage

Settings, Face Time, Turn off Face Time

Restart the phone.

Settings, Messages, Turn on iMessage, SMS, MMS

Settings, Face Time, Turn on Face Time