Here are some steps to try in order to resolve your phone dropping calls:

1. Check your device settings and verify the settings necessary for your carrier type and region.
2. Check the signal strength indicators to make sure that your device is receiving enough signal.
3. Verify that you are currently in an area with good signal coverage.
4. Turn off any applications that might be using your phone's radio when you make a call (such as Wi-Fi or Bluetooth).
5. Restart your device.
6. Perform a factory reset on your phone.