Greetings Myheartisbroken,
If you are having difficulty with calls on other devices, check the settings for each device involved, using this resource as a guideline:
Make and receive phone calls on Mac or iPad - Apple Support
"Set up iPhone Cellular Calls
Make sure that your Mac, iPhone, and iPad meet the Continuity system requirements.
Your devices must also be near each other and set up as follows:
- Each device is signed in with the same Apple ID.
- Each device is signed in to FaceTime with the same Apple ID.
- Each device has Wi-Fi turned on.
- Each device is connected to the same network using Wi-Fi or Ethernet.
- On your iPhone, go to Settings > Phone > Calls on Other Devices, then turn on Allow Calls on Other Devices.
- On your iPad, go to Settings > FaceTime > Calls from iPhone, then turn on Calls from iPhone.
- On your Mac, open the FaceTime app, choose FaceTime > Settings (or Preferences), then select Calls From iPhone.
If your carrier supports Wi-Fi calling on other devices, you can set up those devices to make and receive calls even when your iPhone isn't turned on or nearby. Learn about Wi-Fi calling."
Take care.