Sprint is taking an aggressive approach to competing with AT&T after being denied the opportunity to market its latest offer on DirecTV."We understand DirecTV is now part of AT&T," Sprint spokesman David Tovar said, referring to the $48.5 billion acquisition AT&T(NYSE: T) recently made. "But we thought that AT&T would be supportive of a competitive marketplace and would allow the free exchange of ideas."After Sprint’s attempts to buy advertising on DirecTV failed, the company has launched a new marketing campaign calling out AT&T by publishing the letter by Kevin Crull, who joined Sprint as chief marketing officer in May, sent to Randall Stevenson, AT&T CEO, and John Stankey, CEO of AT&T Entertainment & Internet Services at AT&T. The ad, which reiterates the offer, ran Thursday in major publications across the nation.