All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
If the access to the internet is your exclusive right and you offered access to those around you without a binding contract such as Ijaarah (lease), then you have the right to cut off their connection for any given reason because you alone have the right to use the connection and you are entitled to dispose of it as you wish.
However, if the right to the internet connection belongs to those around you, then it is impermissible for you to transgress against their right by cutting off their connection without their knowledge. The fact that you use the internet for studying or that they use it in committing sins does not justify transgressing against their right and cutting off their connection.
Allah knows best.