iPhone ringtone rings twice when getting a group Facetime call

Hello blaque_tea,

Welcome to Apple Support Communities. 

We understand that your iPhone rings twice when receiving a FaceTime call. We are happy to help.

Please use the steps as listed here to restart your iPhone: Restart your iPhone - Apple Support

1. Press and hold either volume button and the side button until the power-off slider appears.
2. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
3. To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo.

Apple ha recently released an iOS update. We recommend you use the steps listed here to update your iPhone: Update your iPhone or iPad - Apple Support

Update your iPhone or iPad wirelessly

1. Back up your device using iCloud or your computer.
2. Plug your device into power and connect to the internet with Wi-Fi.
3. Go to Settings > General, then tap Software Update.
4. If you see more than one software update option available, choose the one that you want to install.
5. 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.

Let us know if you have further questions.

Take care.