Stop forwarding ppp0 to wlan0

[jeronimo]

Is your feature request related to a problem? Please describe.
Iridium satellite phone data via ppp0 is only 2.4kbps and I do not want it to be shared on wlan0 devices but only on rasp itself.

Describe the solution you'd like
RaspAP allows to forward only eth0 to wla0 or does let to block ppp0 from forwarding.

Describe alternatives you've considered
My knowledge of iptables is nearly zero so I am worried to experiment and break down the whole system.

[jeronimo]

Update, have done:
iptables --table nat -A POSTROUTING --out-interface eth0 -j MASQUERADE
iptables -t nat --delete POSTROUTING 1
iptables-save
But after reboot it went back to -A POSTROUTING -j MASQUERADE