Basically, what this android secret code does is that it helps to cancel if your phone calls are on call forwarding.
What's call forwarding?
Basically, call forwarding is the process of listening to your calls, fax, messages, ETC.
This simply means the third party will be listening and monitoring everything thing you do on your phone.
If your phone is on this problem then, this will be the solution for you.
Watch how to do this with this Android secret Code