You make an appointment to see the prison director. When you see him, you explain what has been happening and that the drugs mafia thugs are making your life a misery. You plead with him to give you special protection.
The prison director just stares back at you in amazement, and then bursts out laughing. He tells you he wouldn't dream of giving any prisoner special protection against the other prisoners - where do you think you are, at a holiday camp? Prison is punishment, and violence from other prisoners is part of it. Medical care in the prison hospital is available if anyone goes too far.
Still chuckling, he sends you back to your cell, where a mafia thug is waiting to beat you up again.
Learn karate from a prison library book
Sit out your sentence trying to avoid the drugs mafia
Try to reason with the drugs mafia