Oklahoma is an at will employment state so unless you have a contract or written agreement that would be your schedule, than will be tough for you. An employer can change hours and shifts to suit their business as long as it is not some type of scheme to get rid of employees for discriminatory reasons.
If they terminate you, you may be able to collect unemployment if you can show that the termination was not due to job performance but them changing the hours of employment to ones you could not work.
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