RM, I hope you get a satisfactory answer to this soon. It makes a huge difference whether he is in a real "prison" (State-run institution) or in a local county jail. State-operated institutions have strict rules and legal guidelines we have to operate by, but county jails can vary widely and a lot of them pretty much do what they want to.
It may be different where your son is, but in the State-run institutions, we are only allowed to give up to thirty days segregation as punishment for any one disciplinary offense, and during that time they are not allowed to have visitors. There are exceptions though. If they are written up and found guilty of certain drug offenses, it can carry a mandatory six-month suspension of visiting privileges. This is mostly for the ones who fail the random routine drug testing, or ones who have been caught trying to have drugs smuggled into the institution ... usually by their visitors. They are not necessarily segregated (locked up) during this six months, but their visits are suspended. They are still allowed to make phone calls though, at certain specified times. If you want to talk to the person "in charge", I would wait till Monday to call. Very seldom is the person "in charge" there on weekends. These people work the GOOD hours, not the weekends!
A county jail is a whole different ball park though. And from what I have seen where I live, it makes a big difference if it's a larger, better funded jail, or a smaller one on a tight budget. Some of the smaller ones may have no funds allotted at all for mental health issues. I live in a small, rural county with constant budget problems, finger pointing and political bickering involving the county jail. County budgets are done a year at a time, in advance, with only a certain amount of $$$ allotted to medical expenses for inmates in the jail. This last year their ENTIRE budget was spent on medical expenses for two inmates with serious (self-induced) problems and nothing was left for anything else. Not that it's right, but in instances like that, mental health issues would come in a very distant second in their priorities. I hope you get some answers soon.