When did businesses first use telephones?
Most large businesses started to use telephones as soon as they became available, as the advantages are so great. Important public services such as the police were also among the early users. Obviously, in the very early years it was usually only possible to make local calls. Moreover, even where long distance calls were possible they were extremely expensive. The ordinary postal service remained the standard means of communication over distance for several more decades.
You could have private conversations with people
You didn't have to go to a person's house to talk to them