John Mayer behind Jessica-Tony split

London, (ANI): American singer Jessica Simpson was allegedly dumped by Dallas Cowboys quarterback Tony Romo after he found text messages from her ex-lover John Mayer on her cell phone.

The two are said to have split up last week, with Romo, 29, ending the 20-month relationship on the eve of Simpson's 29th birthday on July 10. Though the two have not confirmed the break-up, reports suggest Romo dumped the singer when he discovered she was still in touch with rocker Mayer, from whom she split in 2007.

“They (Simpson and Romo) were hanging out and he picked up her phone and she got defensive about it," the Daily Star quoted a source as telling RadarOnline.com. “Tony found messages from John and went ballistic. He dumped her right then. He walked out and that was it," the source added.