H&J Contracting H&J does not pay in a timely manner. I have been waiting 10 months for my retainage Wellington, Florida

H&J Contracting had a Contract with the City of Fort Lauderdale for the Northwest Improvements. We were a subcontractor to H&J for the project in 2010. The project had certified payroll. Which we followed up with the paper work.
In July 2010 I submiitted an invoice for $5,200.00 August H&J paid $4,680.00 They said they were holding 10% retainage. In October 2010 I invoice them for the balance of $520.00 I have emailed nurmous times about the retainage, They emailed me back saying they have not received there retainage from the City. I have emailed them again, but now they won't respond.
You think a Company that boast it does projects from $500,000.00 to $1,000,000.00 per projects. It is now August 2011 You would think they could pay $520.00 to the subcontractor. H&J Contracting does not pay in a Timely manner. If I were subcontractor I would not work for them.