Generally these devices do not allow you to set up static routes, as the Service Providers lock it down in their firmware versions.
1st prize would be to add a static route for 172.16.0.0 with subnet mask of 255.240.0.0
if you are not able to do this, you would need to disable the wifi on the Vodacom router and purchase a device like the HAP Lite or better. With this you would then connect the VC Router and the Router connecting to the WUG. This would also then do your internal Wifi