How do I disable call forwarding when unreachable on iPhone?

To disable call forwarding when unreachable on your iPhone, dial ##62# and press the call button. This will deactivate call forwarding for incoming calls when your phone is unreachable. 

Here's a more detailed explanation:

• Open the Dialpad: Go to the Phone app and open the dialpad. 
• Dial the Code: Enter ##62#. 
• Press the Call Button: Tap the call button to initiate the call. 
• Confirmation: You should receive a notification or hear a beep confirming that call forwarding has been turned off for unreachable calls.