Next time you text a friend to complain that your four-star dinner was only worthy of two stars, think of Joel Metz.

Three years ago, while repairing a cellphone tower in Kentucky, the 28-year-old was hit by an errant cable. It decapitated Metz and left his headless body swinging some 240 feet in the air, still attached to the tower by his harness.

Since 2013, 35 cell-tower repair workers and builders have been killed so companies like Sprint, Verizon and AT&T can satisfy customers who freak when the bars decrease on their iPhones.

In his book “Tower Dog: Life Inside the Deadliest Job in America” (Soft Skull Press, out April 25), Douglas Scott Delaney offers an inside look at the profession that, in 2008, the head of US Occupational Safety & Health (OSHA) called “the most dangerous job in America.” Workers have perished after falling off of towers, dropping out of baskets attached to cranes, and being hit by falling debris. Occasionally, they even get electrocuted to death.

Delaney, 55, refers to himself and his fellow workers — some 15,000 people nationwide — as “tower dogs.” They comprise an industry that builds and maintains the 215,000 cellular towers, rising as high as 2,000 feet each, that ribbon the United States. These men and a small number of women toil for an average of $18 per hour while dealing with snow, rain, subzero temperatures and gale-force winds.

“A tower goes down, the cellphone companies start losing thousands of dollars per second and somebody has to fix it,” said Delaney, who entered the field in 1997 after years spent in Hollywood as a struggling screenwriter. Even if ice is falling from the sky, he added, “there’s no waiting for a day when conditions are better and the work will be safer . . . The cost of having a clear cell signal is blood and lives.”

Delaney, who lives in Reading, Kan., took his first climb during the dead of winter when the ground temperature hovered at 22 degrees Fahrenheit. By the time he cleared the tree-line, a stinging wind-chill-factor stomped the temp down to minus 8. Winds gusted at 45 mph.

He spent 11 hours up there even after he had what he called a “two-second heart attack,” when the belt holding him in place slipped by about an inch. “It slides down the steel and you feel like your body will not stop dropping,” he said. “The two seconds feel like two minutes and you think it’s all over.”

But the worst was when he was helping build a tower.

“We’re putting on 2,000 pounds of steel,” one circular piece at a time, Delaney recalled. “While I was tied on [to the ascending tower] with a leather harness, a 2,000-pound piece of steel hit me and I got turned upside down. Think about being hundreds of feet in the air and getting knocked on your ass . . . “I felt like a turtle on its back. I spent the next few minutes straining to get myself righted. Then I resumed working. What else was I going to do?”

He considers getting struck by lighting an inevitable occupational hazard. “It happens to most of us,” Delaney said, pointing out that there is an upside to hugging a steel tube as the bolts strike.

“When you are on the tower, you are part of the equipment. Your hair stands on end, your muscles ache, but the lightning goes right through you.” Meanwhile, “Guys on the bottom get thrown 20 feet and feel more beaten up the next day.”

They don’t complain, however, because they are the lucky ones.

Delaney added that 96 percent of cellphone-tower deaths (in 2016, seven climbers perished) are preventable, caused by faulty or misused equipment, and workers who take shortcuts. In one case, a tower dog plunged 150 feet to his death when he decided to speed his descent by rappelling down a tower rather than going rung-by-rung with an attached harness continuously protecting him.

“When somebody dies [by being careless] that we don’t know, we say, ‘Stupid son of a bitch,’ ” Delaney said. “But when someone gets killed over something that [he] couldn’t control — that is what puts gray hairs on our heads.”