That situation stinks, and any libertarian would agree — because it has nothing to do with #libertarianism or #FreeMarkets.
One of the tenets of libertarianism is free association and the sacredness of contracts. Either you ceded your rights to negotiate with ISPs to your apartment complex (check your contract), or you didn't, in which case what they did is illegal and you should be able to revert the situation (and all libertarians will cheer for you).
Note that the polar opposite to a “free-market libertarian dream” here would be much worse: ISPs would be all public, or there would be just one ISP, or the government could mandate what ISP you use and how, and you would be definitely stuck with that.