Longman Dictionary of Contemporary English
chat line
noun
EXAMPLES FROM CORPUS
▪ His new book, Vox, is the story of two strangers who meet on a telephone chat line.
▪ Or a chat line, except you don't get done for the phone bills.
Wiktionary
chat line
n. (alternative spelling of chatline English)
Wikipedia
Chat line
Chat line services make it possible for people to communicate with one another by telephone call. However, recent chat lines are like CB radio in which a number of people both listen and speak together.