What are my options if my previous employer is trying not to pay me for the last 4 days that I worked?

I was discharged from my previous position on March 16th at roughly 3pm. The last paycheck that I received was for the week ending March 10th and dated March 17th. I worked the following Monday March 13th, that Tuesday was a company mandated snow day and I called in sick on Wednesday the 15th returning to work on Thursday the 16th. I have yet to be compensated for the final 4 days I worked and when I contacted HR, I was pretty much brushed off with the HR Director attempting to passed off the check dated March 17th as my final pay. All I want is to be paid for those final four days, and my last email to HR went unanswered.