I've done all of that 2-3 times now. its all the same, imac works but the machine i use most the MBPr does not.-Turn off WiFi calling if it is enabled.
-Make sure iPhone Cellular Calls is switched on(Check both devices)
iPhone: Settings---->Facetime---->iPhone Cellular Calls
Mac: Facetime---->Preferences---->Iphone Cellular Calls
-Make sure the Caller ID is set as your phone number
-Log out of iCloud on your Mac and your iPhone.
-Log back into iCloud on your devices.
-Make sure you're connected to the same Wi-Fi Network.