Q: Any suggestions as to why my iphone4 suddenly, at full power , will not send or receive texts or make or receive calls?

Hey peterss2,

I found the following steps for when you're experiencing issues making or receiving calls. If you haven't already, I would start your troubleshooting here:

Follow the steps below to resolve this issue. Please test after each step.

1. Toggle airplane mode: Tap Settings > Enable Airplane Mode, wait five seconds, then turn off airplane mode.
2. Check your phone settings:
   • Check your Do Not Disturb settings: Tap Settings > Do Not Disturb.
   • Check for any blocked phone numbers: Tap Settings > Phone > Blocked.
   • See if Call Forwarding is turned on: Tap Settings > Phone > Call Forwarding.
3. Ensure that your software is up to date:
   1. Check for a carrier settings update.
   2. Check for an iOS software update.
      Note: Some updates may require a Wi-Fi connection.
4. If the iPhone has a SIM card, reseat the SIM card.
5. If the iPhone 4 or iPhone 4s is on the Verizon network, dial *228 from the iPhone and select option 2 to update the Preferred Roaming List (PRL). The PRL determines the cellular towers the phone uses for cellular service, selecting those with the best signal strength.
6. Reset the network settings: Tap Settings > General > Reset > Reset Network Settings.
7. Try to make or receive calls in another location.
8. Attempt to isolate to one network band:
   • If you're having the issue on LTE, disable LTE, if possible, and try again.
   • If you're having the issue on 3G/4G, disable 3G/4G, if possible, and try again.
9. Contact the carrier to check the following:
   • Your account is properly configured to use the specific iPhone that has the issue.
   • There are no localized service outages.
   • Your account doesn't have a billing-related block.
   • Your calls don't have errors on the carrier system.
10. Restore the phone as new.

via: iPhone: Troubleshooting issues making or receiving calls

https://support.apple.com/kb/TS3406

Have a good one,

Delgadoh