A spywitness at the Sunset Marquis in West Hollywood overheard singer John Mayer yelling, via cell phone at on-again, off-again GF Jessica Simpson to “Go Away.”

The hotel guest claims “He said ‘Jess’ a bunch of times, so I would think he was talking to Jessica Simpson. He looked wiped out, circles under his eyes, and some pal was grabbing him coffee while he was having this fight over the phone. There was a lot I couldn’t hear, but at the end before he hung up, he told her to stop calling, stop texting, stop all of it — leave me alone! He was shaking his head back and forth like, ‘God, make her stop,’ and his friend was sort of chuckling at him.”

Jessica has reportedly been following John around like a lost puppy.

This news comes right on the heels of reports that Jessica’s star power may be winding down. According to a popular weekly mag: “We’re doing focus groups and the girls don’t like her and don’t want to read about her.”