@haimeh
So I never actually had to add the route ... it seems the OTA17 fixed my issue (but no all issues). One other thing I did around the time, although don't think this has anything to do with was something I stumbled on while troubleshooting:
/usr/share/ofono/scripts/set-context-property 0 Protocol IP
Here are the route tables for 3G & 4G with WIFI on: (hope the formatting holds!):
3G & Wireless
default 10.x.1.1 0.0.0.0 UG 600 0 0 wlan0
default 10.xx.xx.20x 0.0.0.0 UG 700 0 0 rmnet_data1
10.x.1.1 * 255.255.255.0 U 600 0 0 wlan0
10.xx.xx.20x * 255.255.255.255 UH 700 0 0 rmnet_data1
192.168.250.0 * 255.255.255.0 U 0 0 0 anbox0
4G & Wireless
default 10.x.1.1 0.0.0.0 UG 600 0 0 wlan0
default 10.2xx.x6.2x5 0.0.0.0 UG 700 0 0 rmnet_data2
10.x.1.0 * 255.255.255.0 U 600 0 0 wlan0
10.2xx.x6.2x5 * 255.255.255.255 UH 700 0 0 rmnet_data2
192.168.250.0 * 255.255.255.0 U 0 0 0 anbox0
Not sure if rmnet_data1 and 2 are standard across all phones /connections. If not, you should be able to spot yours by tailing the logfile...
Hope this helps!
PS: to check if you are on OTA17: SystemSettings> About OS should have Ubuntu 16.04(OTA-17)