Wireless phone service is weak, spotty, or non-existent on parts of the Oregon coast. That's why this site is so simple.
The coast between Cape Perpetua and Heceta Head offers essentially no service for my Verizon phone.
In 2017 I found unusably weak reception at the Bullards Beach State Park campground, along the Elk River, and at parks up and down the coast. I enjoy being unreachable at times, but the traveler should be aware. We tend to take our modern miracle devices for granted nowadays.
In many locations, you can find a usable signal by leaving the uneven terrain of coastal dunes and hills and walking out onto the beach. Line-of-sight cell phone signals can travel quite some distance from the next town over beach or open ocean.