Guides like this are useful for people who feel they are being bullied at work.
http://www.bullyonline.org/action/action.htm
For example you should keep a log and inform HR
As has been said, an employee can be dismissed for almost any reason during the first 12 months with an employer. Exceptions include dismissal based on race and or gender.
Dismissal notifications by text/email are used occasionally but usually just as a way of communicating quickly. I would advise an employer who does this to confirm it asap in writing