Liza Colburn uses her cellphone constantly.

She taps out her grocery lists, records voice memos, listens to music at the gym, tracks her caloric intake and posts frequent updates to her Twitter and Facebook accounts.

The one thing she doesn’t use her cellphone for? Making calls.

“I probably only talk to someone verbally on it once a week,” said Mrs. Colburn, a 40-year-old marketing consultant in Canton, Mass., who has an iPhone.

For many Americans, cellphones have become irreplaceable tools to manage their lives and stay connected to the outside world, their families and networks of friends online. But increasingly, by several measures, that does not mean talking on them very much.

For example, although almost 90 percent of households in the United States now have a cellphone, the growth in voice minutes used by consumers has stagnated, according to government and industry data.