Yes, using mobile in the hostel is prohibited at Bishop Heber College. But most students use it secretly. The wardens of boys hostel don’t really mind is students are using mobiles. Rules in girl's hostels are comparably strict. 

If you get caught using mobile, you will have to pay a fine of INR 1,000 and write an apology letter. If you have written 3 apology letters, you will have to leave the hostel.