I've tried to explain that I use Linux to my old ISP, reliance broadband that i had before, MTNL as well. No luck. Mostly I get it done in windows and do the rest myself for Linux.
Most of them are not able to do it. two things to configure: ip and then some setup from web browser for the router. So with some tech from my side they are able to configure the ip. But mostly it might happen that we ourselves may not be sure of the words. The guys who come from ISP will have a visual idea that they gotta put this in that place. So a different GUI just messes their heads.
Frankly its wrong of us to ask them to know Linux when 95% people they go to are on windows. Most computer engineers aren't into linux and we can't expect the 5k-10k salaried guy from the ISP to be a linux wiz. with every one having a diff distro/desktop environment/versions, he would probably rather do engineering itself.