iPhone 5 making and receiving calls

Hi there Mip,

If I understand correctly you are unable to make or receive phone calls intermittently until you restart it. Then it seems to work for a while. I would use the rest of the troubleshooting in the following article to help you troubleshoot the issue here:

If you can't make or receive calls on your iPhone

Update your software

1. Check for a carrier settings update.
2. Check for an iOS software update. Some updates might require a Wi-Fi connection.

Remove and reinsert your SIM card

If your iPhone has a SIM card, remove the SIM card, then reinsert it.

Update your Preferred Roaming List (PRL)

The PRL determines the cellular towers that your iPhone uses for cell service and selects those with the best signal strength.

• If you're on the Verizon network, dial *228 and select option 2.
• If you're on the Sprint network, dial ##873283#.

Contact your carrier

When you contact your carrier, check the following:

• Your account is set up to use your iPhone.
• There aren't any localized service outages.
• Your account doesn't have a billing-related block.
• Your calls don't have errors on the carrier system.

Check your network settings

1. Reset your network settings. Tap Settings > General > Reset > Reset Network Settings. This will erase all current saved settings, including Wi-Fi passwords, preferred networks, and VPN settings.
2. Try to make or receive calls in another location.
3. Switch to a different network band. Tap Settings > Cellular and turn off Enable LTE, 4G, or 3G (this option will depend on your carrier and device model).

Still can't make or receive calls?

If you still can't make or receive calls, restore your iPhone as new.
If restoring doesn't fix the issue, contact Apple Support or take your iPhone to an Apple Retail Store or Authorized Service Provider.

Thank you for using Apple Support Communities.

Cheers,

Sterling