My employer hasn't paid me, any advice?

I was recently working for a company called French Freedom as a courier. I handed in my notice and started to work it and a few days later they fired me. Apparently a customer complained about me. Not sure if this is the case but a little coincidental. They haven't paid me and they are not responding to my e-mails. When I first emailed them about it, he asked me what I did with some of the company's money. I emailed back telling him where it all was and he hasn't replied. This company has a bad reputation for not paying their couriers and I really need this money. Anyone have any tips/ advice on how to get this money?