Thanks Mellow.
It didn't work for me. I get this output: killall: iface-mgr: no process killed
The commands I use (mentioned in my original post) are working fine to switch configurations between most of mobile networks. HOWEVER, it only FAILS when I try to switch to VODAFONE mobile.
Alternatively, I use the Teltonika web interface to switch to Vodafone.
I have no idea why this cannot be done by using Command Lines