Metasploit Android Hacking Over WAN Not Working! Help.

Hi guys!

I am new to hacking. I used the msfvenom to create a payload and sent it to my phone. LHOST was my private IP address and port was 4444, I set up the listener, and it worked.

But, over WAN, when I use my public IP in the payload and private IP in the listener, it doesn't establish a connection with my phone. Why does it happen. Help would be really appreciated.