Alyssa MacKenzie, 32, rarely used her smartphone to make phone calls, apart from the occasional conversation for her work as a disability rights advocate.

But when the lockdown for the coronavirus set in, Ms. MacKenzie could no longer pop by her mother’s house a few minutes away in New Canaan, Conn. So she has called her multiple times a day, including once recently to get a recipe for pasta e fagioli.

A couple of hours later, she said, they were still talking.

“We started with the recipe, then talked about my younger brother, then my work, then her day, and next thing I knew, the soup was done,” Ms. MacKenzie said. “I needed to hear the familiarity of her voice.”

Phone calls have made a comeback in the pandemic. While the nation’s biggest telecommunications providers prepared for a huge shift toward more internet use from home, what they didn’t expect was an even greater surge in plain old voice calls, a medium that had been going out of fashion for years.