Shorted pay and hours on final paycheck, what do I do?

I voluntarily quit my job and on my final paycheck I was short pay for hours worked due to a glitch in the employers system. Was told a check was in the mail over a week ago and told by employer all I could do was wait, that they can't do anything else. What grounds do I have to stand on? I have bills to pay that I can't push back any further due to this.