You do not provide some operative facts which would better enable responders to address your post. For example, are you an “at-will employee” in the private sector? Are you covered under a union contract, an employment contract or a civil service protection system? These background facts would add important context.
If you are an at-will employee (as are the vast majority of American workers), then you probably do not have any basis for challenging your probation or your current suspension. If you are at-will, your employer could dismiss you without cause irrespective of the terms of your probation. An employer can fire an at-will employee for any reason as long as said reason does not contravene a law or a contract.
The fact your supervisor reportedly did not follow the terms of the probation would not matter. Moreover, his conduct in this regard alone does not constitute cognizable “harassment” under the law.
Indeed, if you are an employee at-will, you are fortunate to still have a job. While three years probation may appear harsh, your employer could have fired you for the circumstances leading to your probation and/or the circumstances leading to your current suspension.
Two additional points/questions: First, why didn’t the representative from Human Resources accept the data information on your phone to establish that you received the text during your break and not during work hours? I do not know of any phone company which delineates the transmission of individual text messages on its customers’ phone bills. If the phone company does not voluntarily turn over this information, there may be no practical means for you to obtain it. Human resources’ request may be impossible for you to fulfill. (If this matter involved a civil or criminal proceeding, a subpoena could force the phone company to produce the information. However, you do not have the apparent basis for a possible civil action here.)
Second, if you return to work, you need to operate like “Caesar’s Wife” as long as you remain employed with this company. Generally, you need to follow the letter and the spirit of all of the company’s rules. In particular, do not take your phone out of your pocket for any reason during work hours in the workplace! Cell phone access is not worth losing a job (at least without a comparable job already lined up).