I highly doubt you're getting fired. It's just a bunch of bullies that, as when they were suckling babes, to today. The only way they know how to get what they want, is by yelling, screaming, throwing, punching, spitting, and threatening.
Transfer to an office that wants you?
Grievances? Can management threaten me? Is management scheduling practice realistic and respectful to all employees? Can management abuse phone privileges? Write your statements.
Get these in asap. Don't get called into the office, you must say; will this lead to discipline?, then request a union rep be present. Get your grievance in before they act, then you'll have a retaliation grievance as well.
NRLCA position will most likely be that you are supposed to be available 24/7...unless you get a good rep. Discipline will be progressive. You should expect a letter of warning, no big deal (ive got 2, 14 day suspensions...bigger deal ?)
Good Luck.