The regulation that forced telephone companies to connect to everyone is good in my books. That is an accessibility concern. If you're going to use that as the analogy, I'd say the content accessibility concern over wireless networks (in this case, T-Mobile) is also being met.

Data caps still apply to all T-Mobile wireless subscribers also, although I can see that the spirit of your argument is that carriers shouldn't try to exert influence over data endpoints (typically referred to as "content"). But, using your same POTS analogy, does this mean that 1-800 toll-free numbers should have been banned or regulated out of existence? The interesting point is that in this case, T-Mobile is working around the FCC Net Neutrality laws by making it clear that this is a free program for specific content partners to participate in; it's like "free toll-free" for content that might appeal the most to consumers (streaming audio and video).