Dumpster service - bulk pricing

[Stone Teran]

I have several apartment buildings and I am constantly jerked around by our dumpster providers, Rumpke and Republic.  Most sites have an 8 yard dumpster emptied weekly.  The dumpster providers tease a low rate and swiftly move in rate increases.  I once took over an apartment building that was managed by a somewhat large property management company and they had a "national rate" (even though they aren't national) that was far lower than what I pay.  Has anyone ever succeeded in getting something like this?  I bug the dumpster providers constantly about the rate increases and would love to lock in a "national rate" but they're not budging.  I need more info and leverage.  I have 8 sites with dumpsters.