Hey there, Cjtlbtpct1.
So dropped calls in most cases will occur due to a few factors including network coverage issues, network performance issues, and the local environment. That isn't always the case, but very often one of those the factors is the catalyst. A good way to make sure that your device is best equipped to complete calls successfully is to start out by making sure it's updated fully. Both your iPhone 12 and 13 should be able to run the latest version of iOS 15. If they're not running that now, we'd suggest backing up and then updating.
Update your iPhone, iPad, or iPod touch wirelessly
- Back up your device using iCloud or your computer.
- Plug your device into power and connect to the internet with Wi-Fi.
- Go to Settings > General, then tap Software Update.
- If you see two software update options available, choose the one that you want to install.
- Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do.
You might see that your device is up to date and that there's an upgrade available. For example, even if your device is up to date with the latest version of iOS 14, there might be an option to upgrade to iOS 15. You might want to upgrade iOS when you pair an accessory with iPhone.
This info is available in Update your iPhone, iPad, or iPod touch wirelessly
You may also want to turn off your iPhone, remove the SIM card from each phone temporarily and then place the SIM card back in and power the devices back on and test. A snippet from Remove or switch the SIM card in your iPhone can be found below:
Find the SIM tray on the left side:
- iPhone 13 Pro
- iPhone 13 Pro Max
- iPhone 13
- iPhone 13 mini
- iPhone 12
- iPhone 12 mini
- iPhone 12 Pro
- iPhone 12 Pro Max
If neither of those steps help, Get Support from Apple directly here.
Be well!