You can check, and update (fill out new Forms W-4) your withholding by using the IRS Online Withholding Estimator, and/or TurboTax's W-4 Calculator. See:
IRS Tax Withholding Estimator
TurboTax W-4 Withholding Calculator
As for any remedy, if you can show that your employer did not withhold according to what was on the W-4 filed with them, you could use that to get the IRS to waive penalties and interest for underpayment, but there is no way to get the amount of your tax liability reduced - that is not dependent upon withholding.
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