What can I do to collect my earned money?

A month ago I gave a two week notice to my employer. I found a job closer to home. They excepted my 2 weeks notice and gave me what I thought was my final paycheck on Friday, Sept 8. When I got home from my last day of work I noticed the pay period was from Wednesday to Wednesday. I did not get paid for my last 2 days worked there. I have called several times left messages no returned phone call back. Its been over a month do I continue fighting for that money? If so what can I do? or do I take it as a lost?