1. Root ur phone (which i guess u did, as u r running 4.1.2 on s-advanced) and install app like autoProxy Lite / ProxyDroid (buy or crack ;))
2. (Better n safer) :-
Go to wifi settings, long press iitd_wifi3 and select modify network, tick advanced settings, enter proxy :-
({xx} = 21 for integrated, 22 for btech, 62 for dual)
PORT : 3128
Install firefox n goto URL (probably bookmark it) :-
({xx} as above)
Login, minimize ur browser, and voila! it works...
NOTE : Procedure 2 works on 4.0+ only...
Rooting works for sure... I use wifi for my apps even on GB (2.3.7) ;)