This does not answer the bigger question of "do we care?" Indeed, we may not, as a policy matter, give a tinker's damn if cell phone companies can charge $15 a month for"all you can eat" text messaging when this has no relationship to the cost (fixed and marginal) of the service. But for God's sake, stop analyzing it as a competition problem! the market works just fine, it's a question of public policy. Until we stop framing policy questions as "enough competition -- yes/no," we are never going to get anywhere in solving real public policy problems.
I will add that similar analysis applies to a number of telecom questions we keep trying to resolve by invoking competition without paying attention to market structure. "When banks compete, you win" turned out to be a really bad policy for the economy as a whole in the long run -- even if in the short term it produced great opportunities for subprime borrowers. The same is true in communications markets as well.