Sling took a shot at Comcast-owned NBC today, charging that — in contrast to ABC, CBS, and Fox — its owned stations won’t accept ads for the Dish Network-owned service’s low-priced streaming TV package.

NBC-owned stations in San Diego, San Francisco and Washington, D.C. specifically rejected the ads, Sling says. The inaugural campaign, introduced last week, playfully likens cable companies to schoolyard bullies that force customers to agree to long-term contracts, and expensive programming bundles with hidden fees and poor customer service. NBC confirmed but had no comment.

“The refusal to air our campaign endorses the ads’ central truth: there are traditional pay-TV players that just don’t get it,” Sling CEO Roger Lynch says in a blog post.

He adds that Comcast “has a demonstrated history of shutting down ideas it doesn’t like or understand, predictably to its benefit and at the expense of consumers. This is why we aggressively fought Comcast’s merger with Time Warner Cable. Our argument? That this massive conglomerate would use its incredible market power in broadband to thwart live Internet video services like Sling TV. Comcast was denied this avenue. Unfortunately, it appears ‘Old TV’ may grasp at any tactic in attempt to preserve the status quo.”

Sling hopes to appeal to millennials and cord cutters with a $20 a month skinny bundle of live, streamed channels including  ESPN, AMC, A&E, TNT, History, TBS, Food Network, HGTV, Cartoon Network, ABC Family, Disney Channel, CNN, Bloomberg TV, Lifetime and Galavisión.

Sling reportedly had about 250,000 subscribers in June. This morning MoffettNathanson Research’s Michael Nathanson said that a research firm counted 207,000 downloads of the Sling app to iOS devices since it launched in February.