Getting the same call on 2 iPhones having the same ID

To disable this

  1. Go to Settings > Phone > Calls on Other Devices.

2.Switch this off on both the phones.

Apple with its new iOS has introduced a feature called Handsoff where you start something on one device and can continue doing that on another device with the same id and same wifi network.

To Disable HandsOff

Go to Setings > General > Handsoff
Switch it off.