Why are PRISONERS kept several to a room? Is this a college dorm? Two to a CELL with random searches once a week. No communal baking, no in-room hot plates, no microwaves, no TV, no internet, no computers.
What's wrong with the prison system? If you can't stop the contraband phones, then do block the signals. As for the prisoners who set fire to their rooms, let them live in it for a while. And certainly deduct the cost of repairs from PA tax holdings.
And everyone participating in the vandalism should have a year added to their sentence. If these prisoners can't behave in jail, what makes you think they'll behave when they get out?
Two to a cell, a very bare cell. It's PRISON.