You should check out the US DOL here

Wage and Hour Division (WHD)

Fact Sheet #22: Hours Worked Under the Fair Labor Standards Act (FLSA)

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Waiting Time:

Whether waiting time is hours worked under the Act depends upon the particular circumstances. Generally, the facts may show that the employee was engaged to wait (which is work time) or the facts may show that the employee was waiting to be engaged (which is not work time). For example, a secretary who reads a book while waiting for dictation or a fireman who plays checkers while waiting for an alarm is working during such periods of inactivity. These employees have been "engaged to wait."

On-Call Time:

An employee who is required to remain on call on the employer's premises is working while "on call." An employee who is required to remain on call at home, or who is allowed to leave a message where he/she can be reached, is not working (in most cases) while on call. Additional constraints on the employee's freedom could require this time to be compensated.

This is how to file a complaint with the DOL.

You can also call the US DOL.

Where to Obtain Additional Information

For additional information, visit our Wage and Hour Division Website: http://www.wagehour.dol.gov and/or call our toll-free information and helpline, available 8 a.m. to 5 p.m. in your time zone, 1-866-4USWAGE (1-866-487-9243).

Discuss this with your senior manager and if that doesn't work, escalate it to the corporate level. If none of that works, then file your complaint. Though, it is possible that they will fire you... at which point you can file for unemployment while you look for another job.