What is restrictive housing and are inmates allowed to make phone calls while in that type of housing?

Restrictive housing is 'solitary confinement', and can be classified as "Administrative Segregation" or "Disciplinary Segregation" which to every inmate is known as, "The Hole" or the SHU (Special Housing Unit). Inmates in the SHU are allowed ONE 15-minute phone call PER WEEK.