I see. Thank you for clarifying this for me, Jackie.
Unless there was a promise that your compensation (including the fuel card) would not decrease during the term of your employment, the employer would typically be permitted to change your compensation rate legally I'm sorry to say. Pursuant to the employment at will doctrine, an employer is not required to maintain the terms of an employee's employment but may modify them at any time absent an agreement to the contrary.
However, given that you are a minority, a female, and it appears you are over the age of 40, there may be grounds to pursue a claim of unlawful discrimination if you are not being compensated as well as other similarly situated non-minority workers, so it may be important to obtain salary information for your colleagues. If that information reveals that you are not being compensated as well as your colleagues, then the employer's statements that you are over-compensated would appear to be false and you could pursue a claim of discrimination with the state Fair Employment and Housing Commission.
If you are being compensated as well or better than they are, then there would typically not be grounds to pursue a legal claim against the employer based on the facts you have provided here.
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